Student or Learner
She freaked out while her boss came in the room suddenly.
Is the "freaked out" used correct? Do we have another word to instead of it?
"Freaked out" is OK although a bit over-dramatic. However, "while" should be "when". You're not referring to an extended period of time. Presumably it was the moment her boss entered the room which made her freak out. I would also move "suddenly".
She freaked out when her boss suddenly entered the room.
(I think she'll be looking for a new job quite soon!)
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.