Well I don't know. I'm not sure why you are so sure that it is "indirect" communication. I think that to be surmising that, you must be going partly on what you know of her and your past history (with her or the family culture generally), and not from the letter itself. Because, OK, there is not enough background there for you to be sure of the background, but if I got that letter, I would take the presents part at face value: she doesn't want any more presents. There could be lots of reasons why, but without some other background to make me suspicious, I would just think "OK fair enough". It seems quite a direct communication to me!
Now of course my tendency to think this is partly because in my family if someone said "I don't need any presents now" they probably would simply mean it. I could very well imagine someone thinking "I already have more toiletries than I think I'll use in the rest of my life" and/or "I don't want you wasting your money on something I don't really want." (This would be very similar to how I think myself.) But if the other person didn't spell that out, then I wouldn't necessarily think there was some other subtext I was supposed to guess - although I can see it would be reassuring to you to have more of a sense of certainty about where she's coming from.
With the "I can manage" thing - again I wouldn't necessarily assume some subtext particularly aimed at you. From my experience of being around people of the generation whose contemporaries are getting frail, the degree to which they can "manage" is (understandably and naturally!) a MAJOR theme, which comes up in conversation regularly, especially with people who they think of as caring about them. It can have lots of backgrounds and subtexts like "And I'm anxious about how much longer this will still be the case", or "And I'm very lucky", or "And I feel a sense of satisfaction in still having my independence at my age". But just the fact that she's mentioning it, I wouldn't take as necessarily meaning any one of those. It could just mean "I am writing to someone who cares about me, and I assume they will want to know how I'm doing, especially as some other people in my situation might not be doing as well as I am".
If this is someone you care about in a loving way aside from being a "duty relative", then (as others up-thread have suggested) in your position I would seriously consider starting to write to her regularly (if you don't already do that), at some frequency which doesn't seem too onerous to you. Like once a month, or if you were up for it then more often. (But err on the side of caution and reliability - don't set up a regular routine which is an effort for you to do, and then miss one when she's started to expect them.) With just general chat about your life, as uncensored as you feel happy sending to her, similar to what you might post to us here on LJ. Without even knowing her I would predict with about 90% certainty that she would be pleased by that. And blackindigo - who I gather does know her - has specifically said that she loves getting letters.
Even if she does regret you not visiting, and even if she never really spells out to you how much pleasure she gets from the letters, odds on you will be talked about favourably behind your back. "And I had a letter from my... [niece or whatever you are], she's been doing [whatever]".
If it's then still bothering you that you still would like to send her presents, then you could say that too - once. "I got the message - you don't want presents - but I still have the wish to send you presents, so do let me know if there's something you do want at some point". But recognise that may be your pleasure and your agenda rather than hers.
no subject
Now of course my tendency to think this is partly because in my family if someone said "I don't need any presents now" they probably would simply mean it. I could very well imagine someone thinking "I already have more toiletries than I think I'll use in the rest of my life" and/or "I don't want you wasting your money on something I don't really want." (This would be very similar to how I think myself.) But if the other person didn't spell that out, then I wouldn't necessarily think there was some other subtext I was supposed to guess - although I can see it would be reassuring to you to have more of a sense of certainty about where she's coming from.
With the "I can manage" thing - again I wouldn't necessarily assume some subtext particularly aimed at you. From my experience of being around people of the generation whose contemporaries are getting frail, the degree to which they can "manage" is (understandably and naturally!) a MAJOR theme, which comes up in conversation regularly, especially with people who they think of as caring about them. It can have lots of backgrounds and subtexts like "And I'm anxious about how much longer this will still be the case", or "And I'm very lucky", or "And I feel a sense of satisfaction in still having my independence at my age". But just the fact that she's mentioning it, I wouldn't take as necessarily meaning any one of those. It could just mean "I am writing to someone who cares about me, and I assume they will want to know how I'm doing, especially as some other people in my situation might not be doing as well as I am".
If this is someone you care about in a loving way aside from being a "duty relative", then (as others up-thread have suggested) in your position I would seriously consider starting to write to her regularly (if you don't already do that), at some frequency which doesn't seem too onerous to you. Like once a month, or if you were up for it then more often. (But err on the side of caution and reliability - don't set up a regular routine which is an effort for you to do, and then miss one when she's started to expect them.) With just general chat about your life, as uncensored as you feel happy sending to her, similar to what you might post to us here on LJ. Without even knowing her I would predict with about 90% certainty that she would be pleased by that. And
Even if she does regret you not visiting, and even if she never really spells out to you how much pleasure she gets from the letters, odds on you will be talked about favourably behind your back. "And I had a letter from my... [niece or whatever you are], she's been doing [whatever]".
If it's then still bothering you that you still would like to send her presents, then you could say that too - once. "I got the message - you don't want presents - but I still have the wish to send you presents, so do let me know if there's something you do want at some point". But recognise that may be your pleasure and your agenda rather than hers.
My 2p - hope that was useful