Anonymous participant 730 frankly if the renter is traveling often and making MANY ENTRIES into Thailand during the rental period, I don't think it's wrong for the landlord to charge a nominal fee for filing the TM30 each time.
ASK her airline what they may require when she flies to Thailand with a return ticket departing 9 months after arrival.
She should not have a problem entering Thailand proof of her relationship with you, your address, phone number and your passport showing main page, your phone number and your current extension of stay.