I don't let anyone come over for good reason.

I let my best friend because she's already seen it all.

We were standing outside the house talking.

She saw my mum knocking on the window waving underwear with both hands and yelling "it's been so long"

Friend: what's your mum waving?
Me: *sigh* underwear
Friend: Nothing out of the ordinary then

Nothing provoked this. This is just her.