She has faith in you. When she refers to you as "bro," it suggests she feels comfortable discussing certain concerns with you. She doesn't have a boyfriend, so she's hoping you're the one she can rely on. In such cases, it is possible that you are in the friend zone. Even if you don't like how she addressed you, don't tell her. If she brings up your name again, simply say you haven't been given the chance yet.
The fact is, most girls don't want to be friends with guys they date. It's not that they're being mean - they just don't want their time or energy wasted. A guy who wants to be friends with his girlfriend/fiancee isn't going to let this stop him from trying to win her over with sweet words and gestures. He knows that talking to her every day won't do, but he still goes out of his way to make her feel special.
If you really like a girl, then you should be willing to risk getting into the friend zone if necessary. Just know that if this happens, it's not the end of the world and there are other girls out there who aren't afraid to give friendly relationships a try.
If a female refers to you as "bro," it suggests she feels at ease with you. She wants to chat to you and tell you about her troubles since she believes you can assist her. She needs a shoulder to weep on and doesn't have a partner, so The Bro is the best option she has to vent to.
A female calling you "brother" shows that she holds you in high regard. She would never call someone else's brother without any reason. It could be your sister or mother, but only if they are not alive. Thus, when a female calls you "brother," it is because she values you and your relationship with them. Even though she may be alone, she isn't lonely because she has her family around her.
If a female calls you "Bhaiya" or "bhai", then it means that you have impressed her very much. You have done something worthy of respect and she would like to show this to you by calling you by your pet name. This is usually done by sisters towards brothers or mothers towards sons.
Calling you "baa" or "baba" means that you have saddened/frightened the female. Perhaps you have done something wrong and she would like to warn you against it. Or maybe she is unable to speak up herself and so she makes another animal sound to let you know how she feels.
It's completely likely that a girl will refer to you as bro since she refers to all of her pals as such. It's just how she refers to those she likes, but in most circumstances, her calling you bro has a different connotation, or she doesn't like you romantically and regards you as nothing more than a buddy, a bro if you will. However, this is not always the case, sometimes girls just call everyone bro, even those they're not friends with.
In fact, according to research done by Vocativ, 90% of women have been called "bro" at some point in their lives. So it's very common for a girl to call a guy she likes a "bro".
However, before you get too excited, there are several things to note. First of all, researchers also found that only 10% of women have been called "bro" and found it offensive. So while it's possible for a girl to say "bro" and it not be derogatory, it's also possible that it could be seen as an insult depending on the context and feelings shared between the two people involved.
Secondly, not every woman feels comfortable being called "bro", especially since many women feel like it implies a friendship that isn't necessarily true. For example, one study showed that almost half of women don't want to be referred to as a "buddy" by men, mainly because they feel like it makes them less attractive compared to other women.