no way! no changing the locks, no turning off utilities, no packing her stuff and moving it out... that will get the couple into a lot of trouble...
A similar situation:
My neighbor let a woman stay at his home because she had nowhere to go. She moved in and stayed. After a few months he could not take it any more and told her to leave. A big argument ensued so the cops were called.
They told him that as long as her driver’s license had that address on it, and it did, and she received mail there, and she did, she could not be thrown out.
She eventually found another sucker to put her up and moved out...................