People may be overestimating how loyal Josy is to Maya at this point in time. I'd argue that she's more attached to the MC.
1. MC didn't know Maya until uni. I think it fair to assume then that Maya probably never visited at all or at least never came to pick Josy up at the store even once during the entire time MC was working there.
2. After week 1, Josy was intending to move even further away and get a clean break. Not something one would do if one wanted to be within a short train ride of her GF.
3. Josy was surprised and happy when MC told her he'd come home to visit. The trip also gave her some 2nd thoughts about leaving. Who didn't give her 2nd thoughts? Someone for whom visiting Josy didn't cross her mind despite being exactly the same distance away as the MC.
4. Josy called the MC first asking to stay with him and promising to explain all face-to-face. (Sounds very much like an "I pick you" conversation in the making to me.) Unfortunately, campus hobo had no abode of his own. Staying with Maya was her second fall-back choice.
Not blaming anyone here, perhaps Maya was keeping a low profile due to her dad, just that, as a result, the MC seems to be a bigger influencer for Josy now. Thus, if MC tells her not to join the HoTs (in addition to Tommy's objection) she may be more inclined to follow his advice than Mayas.
I'm probably boring everybody but whole Maya+Josy thing is another plot hole. I won't even bother with how NOTHING pointed that Josy is with Maya - cause DPC deliberately changed facts so people wouldn't look at obvious - not caring about inconsistencies.
Think about - Josy is complaining about how she can't be every week with the person she loves. Really? Cause those 30 minutes by train is an impossible distance?
Now, she is claiming she's in a relationship and doesn't want to do anything with MC cause that would be cheating? That's BS.
Why? Cause Maya said in 0.3 she is ghosted. So, Josy is the one that cut all contacts with Maya - and that means Josy isn't in a relationship anymore. Then what's the point in her "I'm cheating by being with you" thing?!
Not to mention, but that Maya's phone-call (scene used to create false assumption about Maya+Chad) is probably a call from Josy. And if that's the truth, then Maya isn't ghosted.
So - congrats. Logic in that relationship is fucked up any way you look at that.
