Changing my thinking in relationship

I have a dear friend with whom I have an ongoing challenging relationship. I would love to change my thinking about her or about our relationship so that I can change the way I feel and respond.

L. was my first yoga teacher and initially trained me to be a yoga teacher back in 1999-2001. I continued to work with her and study with her until 2004. She has self described as depressed and possibly manic/depressive or borderline. I have observed her ups and downs and also OCD type behavior.
She stopped teaching in about 2006 and since then has had financial difficulties. Actually, she has always had financial difficulties but they have gotten worse since then. She lives in Federal Senior housing and hates it. She talks a lot about being poor (despite having had a privileged upbringing).

Being financially much more well off, I have given her money over the years. I essentially give her a food stipend three or four times a year so that she can purchase organic food. I have given her money towards the purchase of new cars when her old ones are about to die.

Now in her 80s, she relies on me more and more as her primary friend and support (I am in my 40s). She does have another person who also helps her financially and emotionally as well as taking her to medical appointments. (We live on opposite coasts so rarely see each other and only talk on the phone.) She has two sons but they are not helpful to her – they have a lot of issues themselves.

My question, as I stated, is that I want to change the way I think and feel about her. I often feel dread when she texts me, emails me or when she wants to have a phone conversation. I think she would love it if we talked every day but I can barely get myself to schedule something with her once a month. She feels needy and too reliant on me (my thoughts). I confess that I sometimes feel resentful and then I feel bad that I feel resentful – partly because I know that I create this feeling of resentment.

I look forward to hearing to you! I am new to SCS and new to this process.