Basically the story goes like this:
Heavy investment to low investment for no apparent reason
high investment -> good date (fun, making out) -> high investment -> low investment (possibly)
On Thursday (29th) I meet a girl while out in a club with my (male) friend who happens to live in the same student house as the girl. We dance with heavy kino, I number close, we exchange a few texts.
A few days later I text her and almost immediately she suggests to go to a party. We exchange a few playful texts. The next evening we meet, get to know each other better, then go to a club and as we start dancing, almost instantly she starts making out with me; we have a good time, dancing and kissing, I walk her home. Later she texts: "I had a great time, thank you :*".
We text for a bit the next day, she responds quickly, texts are often long; I take my time with replying (actually being busy), but my texts match hers in terms of length. Her last text comes around 4pm, I respond before 7pm (as I was meeting a friend).
Next day I text her in the morning; I get no response so I call in the evening - no response again.
The following day I text her "what's with the radio silence? ", she responds with quite a long text that she was out at a party with my friend 2 days before, had little sleep and went home to her family (a few hours by train away) to help with Easter preparations and went to sleep early. 30 minutes later I message her that considering our recent texting, I though she lost her phone when she didn't respond for a day. With no response I follow up with something else and get a quite a long response 5 hours later. I comment on it the next day (Saturday), but she doesn't text me back, so I stop. Today is Monday, she's coming back from her home town tomorrow.
What's the deal here? How come the girl, previously invested in the interaction, the girl I've had a great time and which I took things a bit further with (making out), suddenly seems uninterested? Or perhaps I'm blowing this out of proportion and it is a case of her being busy with "family life" during Easter (though how hard can it be to spare a few minutes to communicate with someone you apparently enjoy spending time with)? Also I am a bit surprised at how casually she mentioned that she was at a party with my friend (I asked him about it, he claims that he wouldn't mind taking things further, but that nothing happened between them, they were just out for fun). The girl is pretty outgoing, so maybe it doesn't mean anything (my friend and her live on the same floor after all), but it still got me slightly worried. That sudden shift in investment is more worrying though. At no point had I previously sensed any reluctance to communicate with me from her.
What do you think about the situation? Any tips on how I should proceed? For the first time in 4 years I feel like I'm developing oneitis, so I'm planning to resolve this quickly (either way), as I hate the feeling. Reminds me why I don't like to get involved emotionally too much - tbh I don't know what made me get more involved in this case.
(BTW I can provide a longer description, didn't want to scare people off with the wall of text it ended up being :P)