It sounds like you are just getting to know her on a deeper level. Apparently, over the past 2 years, you two really haven't gotten to know each other all that well. Don't set any wedding dates for anytime within the next 12 months. You two need more time before tying any knot.

It does sound like she has some significant emotional problem. Actually, you both behaved badly. (I think you are slightly minimizing your contribution to the fracas.) You sound like the more rational one. You are very right to be seriously concerned about what kind of a partner she'ld be. The mean treatment of a puppy is very worrisome also in the context of what you say.

Apparently she is under a lot of stress in her role of caretaking her granny and is angry and resentful about what she is doing for her. That doesn't justify what she did. It does suggest that she is not mature about how to manage a difficult situation. It also sounds like the two of you don't really confide in each other well. Or, I should say, she does not open up to you about what is bothering her. You do mean a lot to her, or she wouldn't have gotten upset about you leaving.

You need to keep a distance from her, so that she realizes she has to make amends in some way to patch things up. You're not going to be able to push her into counseling. Sounds like she is real resistant to advice. So: make yourself scarce. Let her know that, if this is what she has to offer, then you don't need to be around her. That may be the only way to get her to take a look at her behavior. She is testing you to see what she can get away with. Be careful what precedents you set. You don't want a lifetime of these kind of blowups.