<human>: Condense the text into a few key points

I need some outside perspective...My girlfriend went out last night to celebrate finals with her friends. She said she would get a cab back to the apartment we share around midnight but when I woke up this morning she wasn't here. She finally texted me later this morning and said she got too drunk, her phone died, and went to her female classmate's apartment. 

She hasn't been acting strange lately and is insistent she would never cheat, which I'm inclined to believe as this has never been an issue.  I'm just so hurt and mad, frankly, that I don't know how to get past it or if this is worth ending the relationship over. We've been exchanging texts (I'm at work, typing from my phone, atm) but I'm still really pissed. 

The kicker is I *just* bought an engagement ring last week. I obviously am not considering proposing in the immediate future but I don't know if it would be best to return the ring and get my money back or hold onto it in case we work it out.
<bot>: Girlfriend got too drunk last night and didnt come home or even tell me what she was doing. Not sure how to move past this.