Has anyone done this?? (hacking other peoples twitter.com accounts)

Basically I was dragged onto this site - and I (rather drunkenly) claimed that I hack a persons account and change the background... This is totally harmless - we chat regularly, she loves shoes and has a terrible shoe themed background... All I want is to change that to clogs! (it's the little things that make me smile )

Any suggestions? she is quite web savvy - I tried the basic guesses, i'm looking for a more technical approach.

Peace