Ex-wife owes me money

Location: Texas

Two years ago, my ex-wife and I agreed that our son (14 at the time) could go on an international field trip. He would be responsible for paying half, and she and I would each pay 25% of the cost. These trips are planned 2 years in advance so it gives families time to save money. I paid for the entire trip up front in order to capture an early bird discount that equally benefited all 3 of us. Our son earned and saved enough money to cover his portion. My ex said she would pay me back in full by the time he leaves. Well, he leaves this week and when I asked her about payment, she is now trying to renege on our deal. Her portion is just over $1,250. If she stands firm and refuses to pay her portion, can I go after her in small claims court? I have text messages from her from 2023 where she acknowledged this is a shared expense.