When she returns insist that as soon as you finish your drinks you will leave while you reach for your wallet (to make sure she thinks you really are ready to leave), she will want to get out of that dirty ass restaurant so bad she'll throw back that margarita like a shot of premium tequila.
When you are done with your drinks leave that dirty place in a hurry, you need to get her to a vehicle before she passes out. Once you have her in the car and she passes out take her around to the back of the restaurant and lay her down by the dumpsters.
The muscle relaxers should be in full swing by now, allowing you to slide each of her arms into her own ass (one at a time) when you pull them out there will be bits of nasty putrid shit on each of her smelly little arms, creating the Mexican Long Sleeves.
Its best to do this on a very hot night so that by the time she wakes up the shit will be dried on to her arms and she will have no idea what happened.
Scott: "Haha I have a feeling she won't be back for awhile, I took her out to Sanchez's last night and gave her the old Mexican Long Sleeves."
Wayne: "Not again dude that's the third secretary this month."
Scott: "Stop acting like a Pussy"
PS. After completion of the Mexican Long Sleeves you should probably get the fuck out of dodge because you have just broken some undeniably serious laws, by that time you'll have to take a shit too, just make sure you don't shit near the crime-scene.