My mom did walk in on me and my gf b4 we had kids...she was in between homes and had to stay with us so we gave her a house key. Well it was mine and my girl day off and we wanted to put our kitchen table to proper use 20 mins later in came my mom through the back door me and gf just looked at her she looked back turned around and walked out. She came back to my house about 3 hours later and yelled at me because I didn't shoot her a text. I was like really mom because I'm bout to -blam!- my girl oh wait gotta text mommy. She was like well when it's 3:30 p.m. on a Wednesday that's not a normal time for such activities. That's was the end of the conversation and it's never been spoken of again till now.... Moral of the story never give your mom a house key even if she is living with you, also the only thing better than sex in the afternoon is sex in the morning.