I think most people are assuming this is much more serious than it may actually be. Unless she's especially strong or you're especially weak, I don't see it as any different from yelling. My first ex would hit me when she was angry with me at times. I thought it was adorable. I barely felt it and I knew I could flick her across the room with my pinky if I wanted to. I think this makes it very different.

If she's crying afterwards, it's likely because she's either genuinely ashamed of herself or she's being manipulative. You'll have to decide for yourself what's likely to be the case. None of us can answer that for you because we don't know her like you do. It's possible that her strong emotions coerce those outbursts out of her, but she very much doesn't want to lash out like this and feels deep regret after she does. I wouldn't judge her as manipulative just for this unless it's obvious. If you think that's possibly what's going on, keep it in mind, but I would wait for more evidence to pile up before making such a consequential decision.