You doing your job correctly and getting things done on time is not being a pushover. That's being efficient and professional. Now, if you are super busy at work with a bunch of other tasks that need to be done and boss thinks to herself "Well, I can't find anyone else to do this, so even though I know Stressed Messed is incredibly busy, I'm going to go give this to her anyway because I know she won't say she doesn't have time" Well, then that's her taking advantage and using the word pushover would be considered judgmental.( That's a reflection on her -not you.) However if it's just a matter of giving you the task because she knows your one of her best employees, then that would mean she used a poor word choice. I'd try to let it go and just ask her what she means if she ever uses the term again.