either she's just feeding you this bs so that you will drop the whole tramp thing because she doesn't want you to have it, or she's paranoid as shit. both are just ridiculous. what kind of insurance are we talking about? if its just home owner's insurance i can see her being sketched out about if someone gets hurt shes worried about getting sued, but that never happens.
just because you get a tramp doesn't mean your rates will go up. its like having a summer set up, yeah you can get hurt, but you can get hurt walking down the stairs too. having to tell the insurance company is ridiculous, sounds like your mom just doesn't want you to have one....so just bug her about it till she tells you the truth (that she just doesn't want it), or till she just gives in