If you’re denied upon entry with an onward ticket within 60 days, the immigration can’t blame the airline and demand that they’re responsible for your return as if you didn’t have one. In situations like this the immigration is just looking for a reason to deny you and sometimes just do it the easy way as no onward ticket, no cash or no accommodation.
TM.27 is change of address in Thailand. You apply for 30 days tourist extension on TM.7 and the requirements are only passport with latest stamp, passphoto, 1900 baht cash and TM.30 if your immigration will ask for it as not all do. If she needs to change address, she’ll need to take a couple of nights in a hotel and they’ll make an updated TM.30 for here.
You need a pass photo as well and apply on a TM.7 at the immigration. If your immigration requires a TM.30 which is your host’s responsibility, you might need to take a night in a cheap hotel to get an updated TM.30 address registration. Ask your host to provide you one first, but this is a known problem with AirBnb stays.
If you’re on a real 60 days tourist visa you’ll apply on a TM.86. If it’s 60 days visa exemption you’ll apply on a TM.87. Go to your immigration and get their specific requirements handed over first.
If your current stay isn’t cancelled, you might need to leave to cancel and re-enter on a visa exemption or a tourist visa to apply for a Non O in country.