It doesn't sound like she's trying to prevent him from feeling jealous, she's trying to prevent her living space from becoming hostile.

She said she wants to avoid conflict and hurt feelings, so I would bet that when she rejected him she probably cited . She likely said she wasn't interested in a relationship right now, thinking this would be sufficient to shut him down.

Well now that she actually does have a boyfriend, the initial sadness that couples his acceptance of her rejection could be replaced with hostility, aggression, or worst of all gasp confrontation.

Your girlfriend is hiding behind the concept of being polite in order to maintain convenience in her everyday interactions with her roommate. She says she's trying to preserve his feelings, but she's also trying to preserve hers. Honest rejection is often accompanied with guilt not to mention awkwardness in her household.

Lots of people, especially women, hold these beliefs and and exhaust themselves for the sake of others and in the end, it's all for nothing because her hiding the truth from him is deceitful and he may be holding on to false hope that his inquiry will secure his spot in her "que" and once she's ready to date, it will be his turn. He's going to resent her for misrepresenting herself.

Again, desperately trying to avoid any sort of unpleasant confrontation under the guise of "manners" is a super common attitude among women Unfortunately for you, this bullshit is internalized so deep in her gendered social identity that she needs to experience the negative side of this for it to really makes sense and for her behavior to truly change.

Also I feel the need to clarify that I understand how being a woman can put you in positions where you feel like you cannot set boundaries because you are afraid. Believe me I get it.

But she is still not handling it well. Fear is real, fear exists for a reason, but she should have a different set of techniques and constructs she uses for that. That's a necessary part of being a woman, it sucks but it's true.

Good luck