WEIRD facebook glitch!? A person I had as a friend it said accepted friend request?

[Megan]

I had this person as a friend already and was creeping on them, all of a sudden a notification pops up that friend request accepted, when I was literally just on their page and had them as a friend for about 5 months? Could they of done something, or was it just a facebook glitch or was it something that i did by accident?
I never added them they friend requested me a long time ago and i accepted a long time ago

[Charles]

that's way it works they invite u to become a friend, u have a to click on except , or not