So I don't get it...

So Caroline is normally a very social little girl, not shy and clingy at all, but when we got her hair trimmed this morning, the moment we stepped inside the place (which we have been to a few times now), she was not happy! She clinged to me like I have never seen before and when we had to start the actual haircut, you would have thought we were physically hurting her. She screamed, cried, reached for me and no amount of snacks, toys, nothing would help. We ended up giving her a lollipop and after a bit it helped and she calmed down. Her reaction to getting her hair cut was just so odd to me and out of character for her. She only reacts that way when we go to the dr. Does anyone else have kids that freak out like this?? Whay do you do?