Hopefully you have receipts for the cash payments. If this goes to court, it will be your word against hers. The judge will decide.
Actively practicing law in Texas. Inactive licenses in Arizona and Georgia. All answers are general in nature and no attorney/client relationship exists in this forum.
You need to look carefully at the lease. The landlord should not normally be allowed to raise rent. If there is a dispute of payment, any receipts should be helpful. The lease should also address the type of payment the landlord can receive.