Is it normal to feel and think this way?

When I go to a friend's house, i get scared that our mutual friend will find out get angry because she aren't invited, and i try everything to make sure that she won't find out. But i only have this issue when i'm with two specific friends. And when i'm with others, i don't mind as much. Like I don't want A to know that i'm hanging out with B and vice versa. It's up to the point that i think of excuses even before anything happen. is this normal? or not at all?? please help