How was Mikaela be written out of Transformers 3?

Answer 1

they didn't pull her out of the movie.. Megan decided to leave because of Michael Bay.

"He wants to be like Hitler on his sets, and he is," she continued. "So he's a nightmare to work for but when you get him away from set, and he's not in director mode, I kind of really enjoy his personality because he's so awkward, so hopelessly awkward." -Megan

Shortly thereafter, members of the " Transformers " crew posted an open letter on the director's site, condemning the actress for her behavior on set, calling Megan, "the grump of the set," as well as "thankless, classless, graceless" and "unfriendly."

Answer 2

I believe for whatever reason she breaks up with Sam and goes on with her life leaving him heartbroken :(

Answer 3

Sam gets a new girlfriend... Mikaela broke up with him