My daughter "Brooke" is a senior in high school. Her mother and I have been separated six years and divorced for three. We maintain a cordial relationship and I am allowed great visitation with my daughter.
I have had a girlfriend for 18 months, "Michelle." We plan on moving in together in April, and I fully expect to invite her to Brooke's graduation ceremony and a party I am hosting and paying for. My ex-wife adamantly states I cannot bring my girlfriend. I think she may use her position as the parent who lives with my daughter to influence Brooke to agree. I don't think Brooke cares. She has met my girlfriend many times and even spent the night at her house once.
How do I handle this situation? I think it is childish for my ex-spouse to insist that the woman I will be living with, and dating for over two years by then, not come. Am I being unreasonable?
No. Divorced couples who remain connected as co-parents eventually have to accept each other's new partners, for the kids' sake if nothing else: They need to see you both let go of grudges, even the legitimate ones.
This doesn't mean you can count to 10 and spring a new love on everyone as if it'll be their fault when they get upset, but you've got years of cushioning.
That said, having a valid point doesn't give you license to dig in — especially not months before the party and before you've run it by Brooke. Your cordial divorce suggests you know this, but I'll say it anyway: It's better to be decent than right.
Because this is your daughter's celebration, not yours, and because your ex-wife's adamance suggests unhealed wounds, the decent move is to try peacemaking first.
Have you asked why your ex is so insistent? Nonconfrontationally, by acknowledging her feelings as valid?: "I know it's difficult. I'd like to think I'd be welcoming of someone new in your life, though, if only to show Brooke I can be. May I ask why the strong objection?"
Then listen. Give empathy a chance.
Then, since you have time, and assuming you don't get the answer you want from your ex, you drop it: "I'll let this rest, and try seeing it from your perspective. I hope you'll do the same for me." Then use these months to be the model of cooperation vs. I'm-right exasperation. It serves your narrow purpose here, yes, and removes some incentive for your ex to manipulate Brooke. But it's also just the right thing to do.
If your ex remains adamant next spring, then offer compromises that don't hit bone. Michelle skips the graduation, for example, but attends the party* with you. Graduations torture spectators anyway, increasingly with each degree of separation from the graduate. (*I'm assuming the party is at a neutral site, because if it's at your home, then it's at her home as of April, and we wouldn't be having this discussion. I hope.)
Or, another compromise: Don't bring Michelle and be clear it's the only time you'll exclude. Why? Because a kid's rite of passage is a lousy time for parents to road-test their contentious, new-partner reality for the first time. You'll still be right next time.