What’s the best way to end my relationship with my girlfriend?

I recently discovered that my girlfriend has autism, which I wasn't aware of when we began our relationship. As time has passed, it's become increasingly noticeable, and I'm struggling with how to handle it. I truly don't want to be insensitive, but I'm finding it difficult to continue, and this situation is starting to overwhelm me. The first time I attempted to break up with her, she went home and harmed herself, which was distressing to witness. In many ways, she behaves quite childishly, and I understand that this is part of her experience with autism. Right now, I'm feeling lost and unsure of what to do. I would appreciate any advice or suggestions. If I come across as insensitive, please let me know. She’s a really nice person, but I’m beginning to feel that we might not be compatible. On our first day together, she told me she loved me, and that has added to my discomfort.