Parking on a sidewalk?

I live in Pennsylvania and have a little problem. I live in a Duplex and lately the people who live on the other side have been parking on the sidewalk out front. I mean, literally on the sidewalk to where they are within an arms reach from the front of our shared porch. We have a driveway big enough to fit all three of their vehicles and the one we have so I'm having a hard time figuring out why she needs to park on the sidewalk out front. It's getting nice out and people can't take a walk or ride bikes because her car is in the way. Today they have all three of their vehicles out there, one on the sidewalk and the other two parked so close to the sidewalk one that if they were to try and get that one out, they would have to drive down the sidewalk quite a ways to do it because of all the vehicles that park out on the street here. The cops drive by and haven't done anything about it so she just keeps doing it. A HUGE problem I have with it is, she doesn't slow down to pull in. she pulls in at the same speed that she drives down the street at and slams on the breaks to stop. If she goes to far past where she wants to park, she puts it in reverse and SPEEDS backwards into the parkin. I'm terrified that when I'm getting my 4 year old off the pre school van that she's going to hit us. Or that she is going to end up in my living room if she keeps doing this. Our town cops are really no help because they have been over there for all kinds of things that other people call about and they just keep doing it without any real punishment. I'm at a loss. The state cops just tell us it's our town cops problem and the town cops don't do anything about it. Are we going to have to wait until she actually runs someone over? Im pretty sure parking on the sidewalk will net you a ticket but they never get one.