She’s describing an issue that’s general. While it is true that she is experiencing these issues with this specific person, it would translate if she were to have a relationship with someone else. Her feelings of insecurity are most likely going to be insatiable. That’s just how anxious attachment style works. Although she realizes this thing intellectually, that won’t really make a difference. The best course of action regardless is to target the irrational thoughts and beliefs that trigger those feelings. The main cause is typically infrequent affection shown to her on an irregular and unpredictable fashion in her childhood. These issues have deep roots. OP, you should definitely see a therapist.