I relapsed from hearing my boyfriends sister purge

I was at a family gathering for my boyfriends side of the family, me, on the road to recovery.. and his sister (recovered?). After having dessert we all mingled around and I was looking for the toilet when I heard her and just, sort of broke.

I didn't tell anyone and it weighs heavily on my conscious. I have never purged. I have tried, never succeeded, but since then I've tried more and more, because apparently I need to be 'better' than her.

It's all so ridiculous. I thought I was over this stupid bullshit. Apparently I'm not. I can't just tell my boyfriend his sister massively triggers me either and I love hanging out with her, she's fun and cool to be around. But I just can't get the sounds out of my head, why can't I be like that? Why can't I have been admitted? Why do I have to struggle while being technically overweight?

Idk. Rant I suppose