[Help] dog behaviour strange after spay

Hi everyone! My rescue mutt Lily is behaving strangely after her spay. She can be spooked occassionally and was very fearful when we got her. There are two people that still scare her and she will growl quietly at them and keep space between them, but then seems to forget and gets petted by them no problem.

Her spay was Wednesday and she has been more fearful and reactive. Today she growled and barked out the window, which she has never done in our apartment before! Our friend came to the front door and she freaked out growling and hiding behind my legs. She normally LOVES this friend.

Is this normal? Am I just a worrying dog mom?