The signatures of Maya and Derek can lose their legitimacy under the legal document if it is proven that the signatures were made by fraudulent misrepresentation of the signatories. So if it is not a normal student loan, as Patrick told Maya and Derek, then the facts of fraudulent misrepresentation are given and can be proven by Maya and Derek, witnesses. The signatures of Maya and Derek therefore lose their validity.
Furthermore, Patrick uses the contract to blackmail Maya. This could lead to the contract being rescinded, as it constitutes blackmail. However, there is a catch, because Patrick could be convicted of blackmail. In this case, it is up to Maya to decide whether she wants to go down this route or not. It's important to remember that Maya knows that her mother Helen is dependent on Patrick and that her father would probably collapse. The only way out of this dilemma would be for Maya to get a lawyer involved and for the lawyer to put pressure on Patrick to pay Maya's tuition fees without Maya having to take the final step of pressing charges for blackmail. But in any case, the relationship between Maya and her father Patrick would be destroyed.