Gabrielle might not win the appeal decision.
Signed documents whenever you received something whether it is monetary, item, services or renting properties are important. As well as billing statements as a proof that you have an amount to be paid. Courts recognize these documents as evidence that there is a transaction involved. This is also applicable to renting businesses. Gabrielle should have issued signed billing statement to Antonio as a proof that he has due amount to be settled in his rent. Aside from that, the billing statement should bear Antonio's signature as an evidence that he has received the billing statement and aware of his responsibilities. Together with receipts, these could be presented in court and would really strengthens Gabrielle's argument that Antonio is not paying.