How do you help miserable people?

I am blessed to have maintained a few childhood friendships into adulthood. I love my friends. But a few of them, 1 in particular, are absolutely miserable.

She has been dealt a (relatively) crappy hand in life. Blessed compared to many people though. I’ve tried being soft and kind, I’ve tried being blunt. But at this point it feels like all she does is wallow in her misery. I keep thinking something will change but this has been ongoing for years now. My heart breaks for her but I’m exhausted from constantly talking about her problems and being a shoulder to cry on.

I’m hoping to get some anecdotal advice, hear how other people have handled situations like this.