Something is fishy about that.. I feel like you're missing some pieces to the puzzle.
Her fiance told me she was pretending. He said they've tooken tests and its not true. Which is sad, but I know I shouldn't get upset it just gets to me
First I would say how do you know she's pretending? Then I'd say, either way, yes you're over reacting. Just don't let her or anyone get you upset during pregnancy. You have a miracle growing inside of you, so just try and enjoy it. If your friend is making that up, she needs help she obviously wants attention, and not getting it in the right way.