I see many people have commented, I havent read them all but I have read a lot, telling you to sit them down & tell them this is not on, give rules, tell them to leave etc.... Though if I've read your post correctly it seems many are missing the fact you have tried all of this & it is not working, they have an obvious sense of entitlement.
I have been in an almost identical situation, so can comment having had some experience of it.
Your options are limited because like you say, they refuse to leave & you can't physically remove them, they won't listen to your requests for them to live respectfully in your space, you can't have a conversation with them because they respond aggressively - so let's think about what you can do rather than what you can't.
You can write & you can move their belongings, so begin by writing a list of house rules, this should include everything you require from, the board they should pay, talking to you with respect, to keeping their area & the household areas clean, make sure it's detailed, so don't just put, keep the kitchen tidy, list what that requires. Date this & Ask them to sign it, Its pretty likely they won't sign & they won't follow the rules, so with this you explain, should they not sign & follow the rules they will be requested to leave, so you will also write a notice period, keep it simple, basically saying should you chose to not live by these rules you will be required to vacate the property on (x) date. removing all belongings. Be realistic in the amount of time for them to find somewhere, so four weeks is probably minimum. Again it's unlikely they will do this, so consider days they are unlikely to both be home. Think of it as like a tenancy agreement & eviction notice, though two months is the required length of time for eviction on an actual agreement, this isn't an actual tenancy, its just something that is using a similar structure.
Also totally forget about wanting her to leave but your son to stay, that's not going to happen, their need to be together trumps everything, and frankly his disrespect to you, why would you want that, that would still continue.
Whatever date you have given them to leave, you can peacefully evict them, have someone ready to change all locks, if you need it someone to help remove their belongings & you pack the belongings & put them anywhere outside your property, try to be respectful in that the belongings are safe & protected - though they don't deserve that, you are the adult & it's about doing it the right way.
More useful look up "PEGS" online about CPA child to parent abuse, they can offer advice & support. Parent services are free to access & you can self refer. They have a Facebook page too.
They will help to empower you, coping strategies, confidence building, communication & more.
I'm always happy to chat, if you want to pm, not only have I been there done it, my son & partner did get a place of their own, but then split four months later & I stupidly let him stay temporarily & it started all over again. I won't go on about my experience here because this is about you & I don't want to distract from that, I just want you to know, I get it xx