I like the premise of a contract, perhaps she even being a legal student working on her law degree. ( I am working on elements of that myself for Playing Chauffer, but that one involves a marriage contract modification so I don't think the two would clash.)
If she were studying some form of contractual law she might be able to construct the perfect legal trap for herself as a playful exercise, a binding contract, if you'll pardon the pun. The document and the bearer could be sold to the friend of her choice, or even auctioned off for charity with her "services" going to someone other than who she had in mind.
Could a local fraternity pool their donations and purchase the contract?
It seems to me that she should reap some reward for her sacrifice though, rather than have to pay for the experience, perhaps the one/ones enslaving her to donate his/their time or money to some charitable organization at the successful conclusion. If she couldn't perform as advertised perhaps her contract could contain a clause that she be resold to someone else at the next school break, as in learn how to be the perfect slave, or grow old and beat while practicing.
A shock collar with a "property of" tag could be purchased, and locked on the woman by her own hand to ensure she didn't change her mind once the fun started, her temporary owner in control of the remote for the device. The key locking it on could be mailed to a neutral party with instructions to mail it back after the contract was successfully fulfilled, and a sealed envelope containing some incriminating pictures of the woman in question could also be sent to the same neutral party with instructions to either open and post the contents on the school bulletin board, or destroy the envelope without looking.
All this could be ostensibly for charity, so no matter what one was compelled to do ones conscience could be clear. Also the sent key could unlock the cuffs about her wrists and ankles, ones she had also placed there by her own hand ensuring no claims of criminal intent could be seriously leveled, most especially if the incriminating sent pictures were of the woman locking them closed herself.
This was a fun exercise, thank you for the opportunity, Jackie.