Not taking sides here, but possible reasons for her behaviour:
1) Maybe she was thirsty and hungry at that time? Needed a cold one
2) Maybe she had PMS?
3) Maybe she hates the job but that's what she's got?
4) She has a miserable life and wants to give others a hard time too?
Or
5) She's jealous because you're cute? heheh...joke lang
Whatever the reason/s is no excuse for her to behave like that especially if all the time. Maybe she would be happier selling banana-Q