I'm going through something similar I was with my girlfriend for 3 years. We were living together and planning on getting married, Earlier this year she started acting impulsively. Then a few months ago she broke up with me via text about 2 hours after telling me she loved me. Since then she has been hot and cold saying "I will always love you and miss you." I'm close with her family and do have some mutual friends and they have all said she is not the same and has cut off everyone that cares about and has had public outbursts yelling at family members. She jumped into a relationship immediately after our breakup. I do still love her and hope she gets the help she needs and is able to mend the relationships with her friends and family. For further context she has said she has burned her life to the ground before.
Move on....don't waste your time. It will just keep happening over and over. They can't control it. You will spend the rest of your life trying to be understanding of thier needs but they will never be able to fulfill yours-and rarely will they care if they don't. They have a very difficult time seeing beyond themselves and they will put you on a pedestal one day and hate you the next...then the following week they will be head over heels with another-you will be blamed for that also. It's like being strapped into a roller coaster flying through a hail storm. RUN AWAY IN THE OTHER DIRECTION AND KEEP GOING.