She should be more considerate, but ask her politely to park infront of her own house because you need the parking space infront of your house. BUT, do this in the most polite manner since you are both neighbors. You don't want to have a problem with your neighbor.
She can park where she wants if its the street so just talk to her when she's getting home or getting mail. Just ask hey would you mind if you parked in front of your house I saw it was empty. I'm sure she will be nice about it she prolly doesn't realize it's a problem. Be nice though because she can park there to be rude if he gets pissed. Then drama starts. Good luck. I had terrible neighbors and I would park in front of their house to Piss them off because they would let their dog poop in my yard after I told them a out it.