It would amuse you to bind the young goth and have her wake up begging for mercy, but it would also be premature and counterproductive. If you can get to her computer, who knows what you'll find out? Addresses, physical and virtual? Screen names? Perhaps even some revealing diary entries?
First things first, though. You need to get inside, and you need to do it silently as a ghost doused in mineral oil and wrapped in cotton with three other ghosts standing around shushing it.
Elizabeth's left her window cracked, so you're not worried about setting off any alarms. Working the screen out of the frame, you prop it in the window box of moribund roses and gently slide the window open enough to allow you entrance. It's easier said than done, and you take it very slowly. Any noise is, at the moment, swallowed by the whisper of lush guitar chords, and Elizabeth is very deeply under.
You lower yourself into her room, take a deep breath, and immediately walk to the bedroom door. Out in the dark hallway, you steady yourself and plan exactly how to proceed. Walking quickly through a target area and thinking it over has always worked wonders for your focus.
Once you're in that cold zone of composure, you mentally game things out. You decide to check the rest of the house first, still keeping things quiet. There isn't anyone else home, and no dog. Both of those contingencies had you worried. With free access, you give the place a quick once-over.
In a matter of minutes, you're back at the door to Elizabeth's bedroom. You're still financially embarrassed from pie and pseudo-cappuccino, but Elizabeth's dad used to have a decent Sager tucked away in his study. You're out for revenge, after all. You'll more than likely mail the drives back to him, so he'll lose nothing but the machine itself.
Concerning your return to Liz's bedroom, you:
peek in, she's still asleep, over to her desk, system on, good, put Sager brick on the floor, no password, no encryption, you're right in, very little security, she's already owned, speedily unown as best you can, you didn't bring any of your own tools, spur of the moment job, you grab a copy of Nookular BAT from a site you remember, install it, get things looking proper, grab dad's brick of a notebook, out the window, screen back on and...
Elizabeth shifts in her sleep, but that's all. You check your time. Roughly fifteen minutes, from her window screen off to back on. Not bad. You haven't worked at this level in years, but it still feels good. In fact, you pulled it off so fast that it seems surreal.
What now?