The biggest difference between teenage relationships and adult relationships is the teenager's ability to communicate effectively. Unlike adults who have had time to discover how to communicate with others in general, and with their significant other in particular, teenagers are just beginning to learn these lessons, particularly when it comes to dating relationships. For example, a teenage girl might feel angry with her boyfriend but pretend like nothing is wrong until weeks later when she finally breaks down, or a teenage boy might not be able to express "I love you" to his girlfriend even though he wants to.
The combination of poor communication and budding hormones means that teenage relationships tend to be short-lived but quite intense—which is why your teenager might become very upset after ending a relationship that lasted only a few months. Power struggles often play a big role in teenage relationship dynamics, and you may notice this in your child's early relationships as she begins to discover what it means to be in love. You may also notice that negative feedback from peers will deter your child from a relationship—while alternately, enough parental disapproval can serve to cement the relationship. This is all part of the teenage experience of seeking autonomy and struggling to define personal identity.
As your teen continues to date and learn from experience, her ability to communicate and express her feelings will improve, and her relationships will deepen and grow as a result. You will notice her beginning to feel more comfortable and confident in her worth as a relationship partner, and also beginning to place more value and priority on her partner's feelings and needs. All of this will help your child develop greater maturity and a healthier self-esteem, which means fewer fights and breakups, and more healthy, serious, developed, and adult-like relationships.