I totally agree that what your mom said was nasty.
However, knowing your story, I would not spend resources and energy on a weekend away with a guy who hasn't been following through for you. I would put those resources into finding and affording a place to live away from your nasty, passive-aggressive mother.
I honestly think this depends on the amount of support close by and the willingness of said support.
Also, that was a super crappy, passive agressive, just NASTY thing for your mother to say. What on earth does having a night away kid free have to do with raising your children the other 125% of the time? ITS ONE NIGHT your talking about. Not an entire week. Prolly not even a full 24 hours.
I know the kind of time and effort you spend making your kids your top priority. And for your mom to say something like that is just meant to hurt you. Dont let it. Because someone who talks to their daughter like that has ANY business handing out parenting advice, right? ;-)