I’m blown away by some of the other comments here. There’s no value in having a victim mentality. Have you openly spoken to your manager about your concerns? How it doesn’t feel fair? How you feel you’re being treated? There’s a chance they have no idea. Maybe they’re not that experienced and are just working things out themselves. Or if they seem like the wrong person, is there someone above them you can voice your…
That said, given the circumstances I believe it would be very wise to also proactively pursue different jobs in this case. If nothing else, it will open the OP’s eyes to the fact that jobs are a market and you have far more options than just staying with one company and hoping for the best.
The concerning part is the personal friendship the manager has with the new coworker. This isn’t necessarily a bad thing, but the way the OP has described the situation suggests that there is an in-group and an out-group, and the OP is very clearly not part of the in-group. A different team or company where people are viewed on more equal relationship footings would be a better fit for someone like the OP who is unsure about navigating company dynamics.