So, the middle-aged “Mean Girl" who was laid off in her previous job started working at the bank four months before you did. You were hired by a man you knew from a former employer and that was no secret. That in and of itself could explain why she doesn’t want you to succeed. I didn’t say it was right; I just said it could explain it.
Before your first day on the job, you were likely a topic of conversation. It’s not unusual for the team to hear about someone new. Their talents and background are lauded, and sometimes prior relationships are mentioned. With the wounds still fresh from losing her previous job, MG may have felt threatened. Why were YOU being hired? Were YOU taking her job or future opportunities? As an older employee, she might say to herself, "I’ll be damned if I let a new high potential take my job". This is mere speculation on my part, but being her age myself, it’s a plausible theory. Fear often makes people behave badly, even when they know better.
In any relationship, you have 50% ownership. Her behavior would be cause for coaching and reprimand if I was in charge, but since I'm not, I can only offer you a couple of options and let you decide. Start by checking your gut. Instinctively do you feel you and MG can have a productive conversation?
If yes, send MG an email, (or verbally ask) to schedule a meeting to talk about how the two of you can work together more effectively in the future. Simple as it sounds, I find that taking the initiative to talk with the other party can lead to a positive outcome. It may clear the air and people can move forward. You may want to include your boss in the discussion as a mediator.
If no, go around her and talk to your manager again. Nobody wants to be a snitch, but sometimes you have no other choice. Her behavior is toxic.
Your manager knows about MG's behavior, so leverage your positive relationship dynamics to:
1. Tell your manager you need advice on how to handle the situation with MG. Try to get your boss to take action, or schedule a meeting between the two of you. If she won't, at least you may get a sense of what the hell is happening. And, just because the boss doesn't do anything, don't assume word doesn't get around about MG's behavior to other managers, and possibly HR.
2. If you feel uneasy about approaching MG altogether, and your boss won't do anything ask your manager to talk with MG's manager. Quite frankly, I'm surprised she didn't already. HR can be a great resource, but I would do that only as a last resort. MG's behavior sounds toxic, and it creates tension in your workplace, but it may not violate the bank's harassment policy.
Whatever you do, be prepared. Have specific examples to explain the negative behavior and how it affects you and the team. Stay focused on how improving the professional relationship is good for you, MG, the team and the bank. People often overlook how conflict between two team members impacts everyone around them, so don't do that here.
You sound like a talented, level headed woman, and I wish you the best. I doubt I would make it this long in a similar case (without ranting and raving). For more on this topic read two other posts I wrote: How to Handle a Workplace Bully and another on How to Handle Conflict With an Older Co-worker
Good luck to you and keep in touch.
Your Office Mom