How many days does an owner need to give a renter to move out in Texas?

My mom is vacating a town home for a friend until they find another owner. Basically she's paying them rent so they would not have to pay rent @ the town home and their new home. Today (1/31) they came to her and said she has to move out by 2/28 because someone will be moving in 3/01. Is that "legally" enough time? Is the notice supposed to be 30 days? 60 days?