Hello Dinbravo, welcome to Psych Central.

It does not necessarily mean that her behaviour is due to a mental health issue or disorder. Especially if the behaviour is fitting to the issues at the time. I can see that she was obsessive towards you at the start which could have been 'love.' That's not a disorder. Then the later behaviour of being manipulative towards you can be due to the circumstances at the time, she thought she was pregnant, maybe not but that is a scary thing for a young lone female. She wanted you to support her and take note of the enormity of the situation by lying in order to get you to stand by her. I feel the whole situation very sad indeed, I do hope you never get in such a situation again.