Gf hurt me a while ago and friend is unsupportive - how do I deal with this?

[Smug-Rabbit2]

We have been together for 4 years. She is beautiful, kind, caring, absolutely amazing with children and all of my friends and family adore her (more than they do me). She is a family girl which I love, and I'm very serious about her. She moved in to mine pretty early on, and for the most part our relationship has been the best thing to ever happen to me, she feels the same. Our lives have meshed together well, she introduced me to her family early on (and vice versa) and everyone gets on well. We have such a laugh together, we've shared some incredible memories, and I see my future in her every single day.

I know she'd had periods of feeling really low especially since she'd been working less, aside from some tutoring. She's worked hard on getting her career back in swing. Over a year in to the relationship she started piling on a lot of stress especially during my downtimes. I know this was not intentional - she is very aware of her tendency to overthink and I've told her how to best deal with this including strategies but she'd only keep it up for so long.

She had good weeks where she engages with all her hobbies, but then really bad weeks to follow. On a bad day it used to be very overwhelming. The first time she hit me was after a friend's wedding - we'd both had a lot to drink, I was tired, but she wanted to have sex. We ended up in an argument and she threw her arms out (aimed at me) and caught me on the chest. She felt very bad for it, but a similar thing happened a few weeks later. I told her if it were to happen again we're over.

A few months later we were at a friend's house, drunk and high. She'd been annoyed with me as she felt I'd withheld some information purposely. I hadn't, I just didn't think to tell her. When it was just me and her in the room she told me she felt I didn't care about her, then apparently (in her words) I looked her straight in the eye and said 'you're right, I don't care about you'. If I had said this, it would've been sarcastically. This caused her to come over next to me and plant her hands on my head. I gave her the benefit of the doubt due to the substances - she told me afterwards that she got really paranoid, couldn't control herself and it wasn't me that she saw in that moment. I believed her. After that, she had locked herself away in the bedroom and was sobbing uncontrollably. She then told me that I'm too good for her, she felt she didn't deserve me, and that I shouldn't forgive her.

I know that my gf struggled to express herself maturely. Underneath it all she has the kindest soul. My friends, and their children, are literally obsessed with her. She always told me that this behaviour isn't her, and she started going for therapy after the third incident.

This was three years ago now, and there's been no such thing since. We're in a very good place, and I'm glad I stuck by her side. One of my friends found out about this the other day... no idea how. They told me I should've left the relationship there and then. What do you think?

tl;dr gf hurt me and friend is unhappy that I stayed, how do I move forward?