Here's a thought...
1. Take away her internet rights while at home. If she has a laptop, block it's MAC address on your router from going online, at all (block the wireless and wired addresses). If it's a desktop, remove the NIC, or block those MAC addresses too.
2. Have her get her own internet service into her room. Have her pay for it completely. Then when she gets the notice about being shut off for being a clueless pirate, it doesn't impact you. I would still do #1 to make sure she doesn't piggy-back onto your internet service when that happens.
3. Kick her out... At 20, unless she's going to college close to where you are, and lives at home for that, it's time for her to leave the nest.
I don't have any kids of my own, but saw how my sister and brother-in-law raised my niece and nephew. They caved on so many things when the kids were young that it was disgusting. Things that our parents would never have allowed us to do, were allowed. Or, my sister would discipline the kids, only to have my brother-in-law negate it. Right there at the dinner table too, so the kids knew that if they didn't like what mommy said, daddy would probably remove that punishment. NOT a good thing to do IMO. You need to be of the same mind when disciplining your children. If one parent gives a punishment, the other should not negate it. It gives very bad signals to the children if you do.
As for punishments... My father only hit me once... Once... I really deserved it, and I never did anything bad enough after that to warrant it again. He hit me just one time, but that was enough. Today, if a parent does that, the state gets involved...
It's NOT abuse if the kid does something that no other action will convince them how BAD that action was. Also, when growing up, if one of my parents gave a punishment, the other didn't reverse it. At best, I could plead to get the time frame reduced. But it was up to the parent that gave the punishment in the first place.
IMO, kids today have no clue as to what it was like growing up without all the technology we have. They think they're entitled to it, along with tons of other things, that we didn't have growing up. As adults we have to work to keep what we have, and/or get better things. So many kids don't understand that, or simply don't care. Disgusting...