I worked at a social media marketing agency for a few months, when I went out of town I gave my manager my login information because my clients would sometimes

I worked at a social media marketing agency for a few months, when I went out of town I gave my manager my login information because my clients would sometimes direct message me instead of email (annoying). A few weeks after returning, some of my new messages would already appear open, and Facebook asked me if I logged into my account from a PC ( NEVER!!) at a different location than normal ( near my managers house). I was upset and went to her boss, they said she was just doing her job and that she had every right to check up on company communication.