Being used as an emotional dumping ground

So I F(20) befriended this older woman at work a couple weeks ago. (I can’t give away too much info bc I want to keep my anonymity but basically this line of work is on a job to job basis and it’s not something that’s guaranteed. You also have to go through somewhat of an application process with each job).

At first I was under the impression that we’d just keep each other in the loop with different work opportunities because that’s what she said when she texted me but now it’s kind of spiralled into her using me as an emotional dumping ground…
She keeps sending me these lengthy paragraphs about her abuser and the trauma she has because of that. At first I thought maybe we’d have the kind of friendship where we can both just vent to each other about stuff but the second I tested that to see whether that was the case I basically got brushed off.
I feel bad for her because she has gone through a lot but I don’t think i’m equipped to deal with all of her problems ESPECIALLY considering she’s so much older than me and I have problems of my own to deal with. Like I dont mind being vented to but usually it’s with close friends I already have an established relationship with (+ it’s reciprocal). She asked me if I wanted to go out for dinner with her and I already said yes and I don’t know how to back out of it without hurting her feelings. Any advice?