Early Period? I need help?

Okay. My girlfriend has been having her normal pms symptoms. nothing new. but about a week before her period was due, she thought she was having an early period. she had some blood a little bit darker than normal, but nothing serious. it lasted for a couple of hours and then stopped. it wasnt a heavy flow, but not a real light flow. enough to soak a pad. could this be an early period? there was no other discharge after that. just the few hours of mild bleeding and gone. she still has some cramping and bloating. this has happened before, but not for a couple of months. and when it happened, a few days later, her period came. its about 4 days later and no period. her cycle is not like clockwork. it varies.