My mom REALLY doesn't want me to go to my friend's house?

My mom likes my friend just fine. She's just scared of their house. My friend, let's call her Eve (14 going on 15). She's a trooper. Eve's sister's dad abused her as a kid, her mom left her when she was little. She's a little on the goth side, but she's polite and has a great personality. Eve's birthday is coming up and she wants to have a birthday party. But Eve's stepdad has a friend named... Bob (in his lower-mid 20's). Bob dresses like a hoodlum but seems nice. There was some talk that he had with Eve but it was a rumor started by a jealous girl at my school that likes Bob, so I don't think it's true. My mom doesn't know if she wants me to go to Eve's house because she worries about her stepdad or Bob trying to pull something... I don't have a cell phone, but I can take my dad's. What are your thoughts on this? I love my friend, she's amazing. I really want to go to her birthday party and act like dorks and be vampyres and whatnot. 5-6 other people are going, I know one of them and one is only in 7th grade. But this doesn't really ease my mom's worries. Why should or shouldn't I go?