The Ex

My boyfriend and I have been dating for a few months now and we're serious about each other. But before that, he just got out of a relationship of 11 months and his ex cheated on him and ultimately broke his heart, forcing him to end things. I know he's moved on and loves me more than anything, but it's his ex I'm worried about. She's such a nice person and we were friends before. I've always looked up to her. The last conversation I had with her was about him and she said "I trust you with him". But ever since we started dating, she's been having panic attacks whenever she sees us together or just him in general. Even thinking about him triggers her. I can't help but feel extremely guilty but we can't just avoid her and I know she's been avoiding me because it hurts her. What do I do? Do I talk to her or give her space? Do I just ignore this?