Your lady will have to provide proof that she has a good reason to come back to Thailand ie a job or family and home to come back to and money in the bank account for the holiday to England they will ask for proof, so sorry but I got it wrong so you are looking to move her back for good not a holiday, can I recommend that you take her frist for a holiday as it is a 6 month visa and she will decide if she likes it or not before you go to the trouble
You hit the nail on the head as long as you do as your told at immigration you can stay in Thailand, the minute you upset or disagree with the immigration you are out of the country
Go to immigration and speak to them and give them the landlord's phone number so that they can ring him or you ring him yourself and let the officer speak to your landlord