Search terms: ways to lose custody, visitation rights, ways to lose visitation
So my question is really situational, and I just want some more informed opinions. My female MC is 36, divorced with a six-year-old daughter, but her ex-husband has sole custody and has remarried. She has standard visitation rights, every other weekend, some holidays, etc. The ex is extremely possessive and vindictive and is potentially looking for ways to cross her out of his daughter's life. Female MC is a teacher and in the story she gets involved with a new teacher at her school, who also happens to be way younger than her. I currently have it so she and the ex signed a no overnight guests during visitations thing in their custody arrangements (found the situation online), but it no longer applies to her ex's significant other as he's now married her. On the other hand, female MC is not married obviously and there are several instances where she takes her daughter over to the boyfriend's (the aforementioned teacher) house and stays over.
Now, my main question is, if the ex is spying on her and finds out that she's doing this, is it actually possible for him to get the court to take away her visitation rights? If that's really unrealistic, then I won't make it a plot point. I just want to know if, under the circumstances I've got, it's within the realm of possibility.
Additional information about the boyfriend that the ex can potentially find out: he's 24, is a weapons enthusiast and has several in his house (guns, bows, swords, etc.), was in trouble in high school for being semi-involved in gang activity.
Also, ex has a lot of money to hire really good lawyers, but female MC makes only a modest income and can't do the same.