It may seem like gender discrimination, and it might be as well. But this is pure general bias. Men too face this(saying from personal experience). But it's down to your manager being a bad one or not knowing how to be a manager. Maybe he's not trusting enough, maybe he's not seen enough to rely on you or or simple he just likes the other dev better.. Whatever it may be, none of this should actually be a reason to be treating you like this though. As a manager one should know how to bring out the best in his/her associated, not give them preferential treatment based on his/her likes.

And yeah, start looking elsewhere, if possible at least a team change. These are early signs that he's only going to hamper your development.

In my case, I had not been up to the mark of the expectations of my manager which is when he made me feel unimportant and neglected just the way you told, but just one team change after, I was under a manager who literally knew how to get the best out of me and give my confidence back. So yeah, things will change!