I am sorry to learn of this situation.
My best advice to you is to go to your court and sit in on the small claims calendar before your own hearing so that you can watch the small claims calendar in advance of your own hearing. This will give you a better idea of what to expect, how to address the court, and how to present your evidence.
Focus on the specifics of your claim. Breach of oral contract claims are very straight forward, but you must present evidence to support each element of the claim. Your evidence can be, your testimony, writings (such as text messages between you and the defendant), and circumstantial evidence (such as an excerpt from your bank account showing the withdrawal from your account to make the loan to the defendant - not necessary, but it can help).
- You must show that there was a contract. To form a valid contract each party must exchange "consideration" (in a loan - you give the defendant money (your consideration), in exchange, the defendant agrees to repay you (their promise for future performance). This forms a binding contract
- You must show that the defendant breached the contract. She failed to repay you within the time frame agreed.
Allow the defendant to make their defense that the loan was "excused" by the relationship (what this does is it confirms all of the elements that you already made). When you get the opportunity to rebut the defense, you can then argue that there was no such evidence or testimony that "excused her performance," and that you have text messages that directly "impeach" her testimony (basically call her a liar). Simply because you were dating or in a relationship does not mean that you waived her duty to repay.
For additional help, I do recommend visiting your local law library in preparation for your trial, but this really is a fairly straightforward case. I cannot guarantee you success (litigation bears an "inherent risk" - meaning there is no way to guarantee an outcome), but unless she has some evidence that contradicts the written evidence, she doesn't have much of a defense.