DPC never showed Josy's reaction when Maya opened the door. He just showed it was Josy in the last render of ep. 3, when they were already inside the dorm with Maya introducing Josy to MC and Josy looking at him shocked/down. But since didn't tell MC he will share a dorm with a meathead named Troy, i don't think they will tell Josy that her roommate will be a girl named Maya.
In the dialogue of that evening Maya expresses several times the shock of having seen her, Josy never. we don't know about Troy because Troy was a stranger to us, a name of no importance, but Josy reading Maya's name is different, why should it be a secret? if your name is written there, your roommate's name is also written there.
Both were ready to break up at that moment to stay with MC. In ep. 2, Josy was grounded without phone either for a fight with her dad and Monica or for they found her naked in their bedroom if MC decide sleep with her. Thanks to that she doesn't reply to Maya messages, which makes Maya think Josy is ghosting her and Maya start think in dive in her relationship with MC because, like she told to Derek, things seems way more easy with him. When Josy get her phone back she see Maya's message but doesn't reply because she said was one message more mean than another. That's why she call MC instead Maya to say she is going to B&R and want stay with him in his dorm. So Maya was ready to break up with Josy and stay with MC thinking Josy didn't want talk (and see) her anymore, and Josy was ready to break up with Maya to stay with MC too. But then comes the "plot twist" at the end of ep. 3 because whatever plans Josy had sure didn't include meet her girlfriend and the guy she has a crush in the same dorm right in her first night at B&R.
Yours is a correct reconstruction, but the situation of the two girls is different.
Maya is ready to start a story with MC because she thinks she'll never see Josy again, so it's normal that confronting her changes everything completely, and she's also the one who remains more moderate in her statements towards MC even afterwards.
Josy's situation is different, she knows that she will have to face Maya, that she will find her at BR, the choice she makes between Maya and MC is a conscious choice.
The "offcial" explanation about that is that they were affraid to confess they cheat on each other with MC. Yeah, i know DPC and his writting...
I think so too, but if the girls are afraid to confront about him, how is it conceivable that MC would do it for them when Josy gives him the clear signal that she does not want to talk about it in front of Maya?