How To Tell If Network Priority Is Setup On Router

Is there any way I can tell if an network priority is setup on the router? The last week or so the internet has been unusually slow sometimes, and not slow at all other. I don't have a good relationship with my roommate (network administrator) and I feel she may have put a network priority on the router for her and or her boyfriends computer/s. Is there any way to tell? Is there a particular way in which the internet behaves when a priority is set? I just don't want to pay for the internet if it is not going to work most of the time.