Hmmm, I had a similar situation (not depression related though) where I could have done with a lot of help from a close relative, who did shag all (it was actually commented on by friends of mine that the person in question was useless and they were appalled by it - and they helped me significantly themselves).
That person needed support a few years ago, and is going through something else now.
The previous time, I offered help (but didn't stretch myself too much) and it was actually acknowledged by that person that I could have chosen to "put the knfe in" and that it was great that I didn't. (I felt very smug but a bit guilty about being smug so tried never to show it!)
This time round their issue is still ongoing, again I'm offering help, but I'm not going all out as I know if the situation were reversed there would still be shag all done for me. Plus I've my own family to think of and they always will come first.
I do admire those people who can forgive much, and appear to do it graciously and healthily, but that's not me! if I pushed myself much more I reckon resentment would creep in and I'd be even less helpful in the long run than I am now.
So if I were you I would try to help to some extent, but just as much as you feel comfortable with - i.e. enough to assuage any guilt and to be in some way effective, but not enough that you start to resent it.