Probably your best option is to approach a senior director or VP for your function, someone above this sneaky director's head. Do so as a group. Have your complaint nailed down with examples. Outline the director's unprofessional behavior and why the group doesn't feel it is appropriate that you fall within the director's new domain. She obviously wants to expand her territory. If you don't want to approach a senior director or VP for help in solving this problem, consider approaching the HR Director. Make sure all of this is not a surprise to your current manager; you don't want to blindside them. In approaching the executive for assistance, make sure you know what solution you are seeking. Do you want her to stop trash talking the team? Do you want someone from your team invited to certain meetings? Do you want an assurance that you won't fall under her purview? Something else?