<human>: Can you give me a shortened version of the text?

I am a 17 male and I just started dating a 17 female 4 weeks ago. We've had a bit of a rocky start but she's always seemed faithful, just a little unsure of the relationship (Which maybe should have been a sign). Seven days ago we had a nice long talk and she seemed really committed to the relationship, she's really busy with work (works almost everyday plus school) but wanted to make it work. The day after this she texted me a whole lot and this continued onto friday. Friday we hung out and she seemed a bit odd, but was more than likely just tired. 

Where it gets weird is here: Saturday she blows off hanging out but has a decent excuse. That day she tweets something that caught my eye and was "Forgive and Forget more like forgive and remember not to fuck with that asshole again." (Quick backstory: she had mentioned something about an ex-boyfriend who had hurt her really bad and she had 'forgiven', and oddly enough this same boyfriend she had recently come in contact with again, primarily because of their overly lapping friend groups, or so she told me) Odd, but not disconcerting by itself. She later deleted the tweet. But ever since saturday she has texted me less and less, hasn't tried to hang out with me, and ignored my calls tonight (wednesday). The kicker: I was being a creep on her twitter and noticed she favorited a tweet about fucking with ex-boyfriends every now and again. 

Some more information: This same ex-boyfriend has been referenced a few times for various reasons; and whenever her and I are together and we see him or his car, she gets a big smile on her face and chuckles a bit. 

So /r/relationships, do you think my girlfriend is cheating? And what is the best way to approach this situation?
<bot>: My girlfriend has been getting more and more distant and been making vague references to ex-boyfriends on twitter, is she cheating?