I would like to be able to help you. I appreciate how much detail you put into the question. Historically, it sounds like there could be a connection in her behaviors and hurt. There may be unresolved grief issues and she is texting out of hurt, but projects it as anger. The anger about the relationship ending may be related to a loss of control. If there were boundaries that could not be set, she may actually be angry with herself or even her mother. It is responsible to meet the person who may be involved in your daughter's life. I commend you for being able to do that. I hope you guys can be amicable as parents.
Do you see yourself ever in a future relationship with her? Maybe all of the pettiness or even failed relationships is a form of what we call "reaction formation" which is a defensive mechanism in place. I will send you a link describing common defense mechanisms which may provide insight to you.
Check this link out.
I hope that you will find this helpful and choose to accept the answer so that I can receive credit for responding :)
Further processing is available if necessary. Thank you! Julie
Basically it may be easier to deal with her anger towards you than showing you her hurt or true feelings.
I hope that this has been helpful to you and that you will take the time to review the answer and provide positive feedback. If you need further information, please feel free to continue communicating.
Thank you so much! Julie