One thing you can do to help your situation is to make sure you keep the noise level down. This way if the cops are called and you friend's mom answers the door she can tell the cops that there is nothing going on and that she doesn't consent to searches without a warrant. There's absolutely nothing they can do if she does that.

There is also a video on YouTube that shows some things about handling situations like this...however i can't find the link at the moment, lol.