Falling for someone is not a logical process,that can be quantified by a mathematical equasion
It is something that just clicks.
As Josy was in a long distance relationship with Maya,she started developing feelings for the MC,same way as he was devoloping feelings for her.Everything that followed was a consequence of that feeling already being in place.Josy already made a decision to leave - leave her present life as whole and start over somewhere else.
What caused the internal conflict was that feeling for the MC.
It gets even more more complicated when it comes to M+J,its not that the girls dont care for each other,its that both have difficult circumstances at the moment.Nothing is working out for Josy,from her parents divorce,to not being admitted to college,to crappy job,to not being able to see Maya anywhere as often as she needs to.Maya has her father situation,the financial struggle and also no access to Josy,to make matters even worse Josy loses access to her phone,meaning they cant even comunicate through phone,Maya starts thinking that she got ghosted.
Its not the lack of feelings that causes the growing distance,but the circumstances of both girls causes the distance between them - and at that time comes a guy offering affection and support complicating things even further.
As for purity of Maya`s feelings - I want to remind you Maya and MC started to get closer becuase of the HoT tasks and the promise of free tuition.