Dear Annie: My girlfriend and I have been together for four years, and most of that time has been great. The last year and half, however, has become quite complicated and strained due to her 14-year-old daughter. I’ll call her “Rose.”

When her mother and I got together, Rose was 10, and up until about a year or so ago, she was a great kid. She warmed up to me pretty quickly, and we had fun playing games, goofing around, etc. Of course, we knew things would change as she got into her teen years, but I can’t say either one of us saw this coming.

Over the last year to year and a half, as she has gone through the changes that come with coming of age, she has unfortunately gone from being that great kid to the 14-year-old female version of her self-centered, manipulative, narcissistic father.

She’s very disrespectful — not just to me but even more so to her mother. The way she treats her mother is absolutely appalling. I stopped going over to the house four months ago because the tension in the house when she is there is unbearable.

In the last month, Rose has chosen to live with her father because she hates her mother (and she used to absolutely dread going to her dad’s house). This is a girl who told her therapist she doesn’t care how it makes her mom feel (though she hasn’t seen the therapist in 10 months).

Unfortunately, my girlfriend deals with depression and anxiety issues, and I don’t know how to help her. Rose moving out is best for both of them, and as sad as it is to say, downright estrangement would probably be ideal because they can’t be together and not blow up at each other. My girlfriend broke down crying last night. She feels like she has to walk on eggshells around her daughter.

My question is how do I help her? She needs to kick Rose out (for good) to her father’s house and tell her she’s not welcome in her house and to not contact her, but of course, she can’t bring herself to do it, no matter how badly Rose verbally beats her down. I’m at a loss and don’t know how to help her, and I really worry about her with the toll it is taking. — Helping a Mother of Narcissistic Daughter

Dear Helping: Though you say you’re trying to help, advocating that your girlfriend kick her daughter out of the house and demand no contact is doing quite the opposite.

Rose is 14 years old — an age that comes with a lot of angst, hormonal changes, and parental conflict. The fact that she’s being rude to her mother is sad, of course, but it’s also a tale as old as time and a phase she’ll likely outgrow. What she won’t outgrow, however, is the trauma of being banished from her mother’s house because her mother’s boyfriend would rather not deal with all the trials and tribulations that come with raising a teenager.

The best way to support your girlfriend is to support Rose. Be patient with her. Ask her questions about her life. Convince her to resume therapy. Set healthy boundaries at home.

It won’t be easy, nor will it be a quick fix, but if you truly see a future with your girlfriend, you need to prove that you care about her daughter, too.