am i overreacting ?

so today my hairdresser came over and ended up saying we should get chinese and wine, i’m not really a drinker so she my oh out to get some, several times when he got back they went out for a fag and she was all over him, flashing her boobs etc whilst i was sat in the living room (i can see the back door from my seat) am i just over reacting or is this totally inappropriate ?