My [21m] chronically ill, seemingly socially isolated cousin [20f] asked me to kiss her. I kinda feel bad for her and wish I could help her in any way. What can I do?

First off, I dont want to come off like feeling pity for her, just that she was handed a terrible hand in life and I feel compassion for her suffering.
She's chronically ill (respiratory and joint issues) and is currently studying long distance since she had a flare up and was bed ridden for a while. Before that she would actually go to class.
I visited her yesterday (she lives with her parents, I hadn't seen her in about 2 months, but we chat sometimes) and she was in bed, looking pretty ill. We talked and laughed for a while, then she said she has always had the most fun with me, held my hand and asked me if I would kiss her.
I didn't know how to respond and asked her when she last kissed someone, she laughed and said it was a boy from high school when she was 18. Then there was a silence and she asked me again. I told her I wouldn't and she seemed very, very sad, and her voice choked a bit.
We kept talking for about an hour, we laughed with a few videos she showed me and I left. She gave me a very sad look when I left, from her bed.
That whole interaction really hit me in the feels. She used to be much healthier and active, and while her family really supports her, she just gets more and more ill. It hurts to think how deteriorated her mental health must be to ask me that sort of thing.
I wish I could help her be more healthy and happy. It hurts to see her so sad and isolated.
Is there anything I can do help her? Any way for me to lift her spirits in any way? How should I react if she ever asks me something similar?
tl;dr: Cousin is partially bed ridden from illness. She appears depressed, unmotivated and socially isolated. She asked me to kiss her and I refused, and she was visibly saddened. The whole interaction was sad and I wish I could help her in any way. Is there something I can do?


Source.