My close friend started to call me bro. Does she doubt that I have a crush on her and is trying to remind me that I'm just her friend?

I've met this girl a couple of months ago. Now we're pretty close friends and almost text everyday. I've always found her to be a very good friend and never had a crush on her. She's already in a relationship ship and I totally respect that fact. She Also knows that I have a crush on another girl. Since the past few days she started to call me bro. Like at the end of ever text she adds the bro tag. I don't mind being called a bro by her but since this started recently I've a small doubt. Is she doubting that I have a crush on her recently? And if she is doubting me about having a crush on her, how do I prove that I don't have a crush on her?