DS girlfriend at our house all the time.

I wouldn't be happy with her walking in on work calls, easily solved by you setting boundaries
How would you feel if you son was staying at her house every night?? My advice would to keep him close
Daughter is a daugter for all your life,
A son is a son until he finds a wife

It's not fair on your other child to suddenly have this person being in their home all the time and on top of that to be bossy to them.
That she walks in to your office is really bad. Clear boundaries need to be put in place with your son.
Max of 2 evenings a week for such a new relationship. You and your younger child need to be able to relax in your home without your oldest's girlfriend being constantly there.

Apart from her wandering into your office when I assume you’re working I wouldn’t actually have an issue with this.

the other option is that your DS is never home and they spend all their time at her house.

dd2s boyfriend is here or dd2 is at his. It’s just part of having young adult DC. You kind of need to be welcoming and make their girlfriends/boyfriends welcome and feel at home. I’d always rather be the house the choose to come to.

I would speak to your son. Just say that you do like her but that she can't basically move in. I would limit it to 2/3 nights a week (no more than 2 consecutive), and then he can spend 2/3 nights at hers which leaves 1-3 other nights to do other things/ see other friends/ whatever but basically keep a life beyond each other. I would also him to speak to her about her coming into your office as that is massively inappropriate. Either that or make a "do not come in" sign for the door

You need to talk to your son asap.

You need to put boundaries in place. 2 months is still a very new relationship, she should not have been involved in your family meeting or walking into your office.

Big thing for me that stood out was you said she is bossy towards 16 year old sibling. That’s a big no. It’s his home not hers. It’s his safe place don’t let her take that away from
him.

Why are you allowing this virtual stranger to walk around like she owns the place? Sit the pair of them down and say she can come over max twice a week and she cannot come into your office at all.

Why have you allowed this woman to spend so much time in your home? Lay ground rules and stick to them.

Tell your DS she can stay 2/3 nights a week maximum.

Your DS has to sort out the house rules with her.

I'd hate this OP but saying nothing makes them think its OK. That might be why she's at yours...her parents might have made their feelings clear. You have to get ground rules sorted, what you'll accept and what you won't.

Sit your son down and have a straightforward discussion. Make your boundaries very clear. She's welcome over 2 evenings a week or whatever you're comfortable with. This is a new relationship and she's still a stranger so shouldn't be wandering around your home without permission. Make it very clear that you won't tolerate her bossing your younger son about. I'm sorry about your dog.

Have you actually said anything? If not, why not?

What... just tell her "Get out of my office, don't ever come in here again".

Tell your son that he needs to discuss with others if she's coming over etc or that you all need to limit the time she's around because it's becoming disruptive.

If she bosses the 16yo... tell her to STFU it's his house, not hers.

Speak to your son about it?

There’s nothing wrong with having boundaries - she is walking all over you.

Definitely not ok, speak up now or your future will always look like this.

I wouldn't like this at all OP.

I would find it quite cheeky behaviour to make herself so at home. Even members of my own extended family wouldn't behave like that In my home.

What do you say to her when she comes into your office? And did you not tell her it was a private conversation about your poor dog?

I think yoh need to speak to your DS and agree with him the amount of time you think it's reasonable for this young woman to be in your home. And he needs to talk to her about the need for respecting his family's privacy when she is in your home.

Just tell her.