Minor in Possession: Underage Drinking in Maryland

This past weekend, a friend of mine threw a party in Bethesda MD. There was underage drinking present, but i would like to know something. The cops entered the premises through the backyard and up through the porch. She says she had probable cause to enter because she saw drinking in the basement, but in order to see what was going on in the basement, she would've had to enter the premises, with a warrant she didn't have. I want to know if it is legal for an officer to do that? She entered the grounds without a warrant and based her jursidiction off of something she witnessed while committing a felony. Also, my friends chose to refuse breathalizers. Was that a good idea? I mean, it felt right at the time, but I don't know what will happen in the long run. Basically, my best friend is stuck with a $500 ticket that she can't afford to pay and i want to know if there is any way to contest this ticket seeing as what the cop did was a felony. She also refused to let anyone use the restroom or to answer their cell phone and threatened physical violence on more than one person. Any help you could give me would greatly appreciated.