I'm tired, so will add to my OP tomorrow, but basically I have a colleague who is really passive aggressive. She is the same grade as me, and works in the same Department, but within another unit.
Due to restructuring, I took over her role last year as well as my existing role, when she moved to a different role (she applied for the other role). She refused to do a handover, so I had to learn the role from scratch.
This week alone I have had to address 2 separate issues with her - she asked a member of my team to go to a meeting on her behalf, on the staff member's day off, without any reference to me; the second issue - I have the lead on a particular subject area, and I have discovered that she has been duplicating / undermining the work I do in this area without my knowledge. I have e-mailed her in relation to both issues, and have received very stroppy responses. I have suggested that we need to meet to discuss communication / responsibilities, which she has ignored. I have copied her line manager into e-mails, but her DH is very senior within the organisation, so she has a bit of a free reign, and picks and chooses what she does, and I think her line manager is therefore reluctant to challenge her.
The examples above are just that, only examples, this is an ongoing issue (i.e. over 5 years), and I think there are a number of factors. I think she is very competitive and jealous (I am aware of difficulties she has had with others), and feels threatened that I have been able to subsume her role into mine with ease; I am significantly better qualified than she is; word is that she is struggling to perform in her new role; and I think she is resentful that I have young children and she hasn't been able to have children (sad though this, it's not my fault. Her behaviour towards me saw a very marked negative change when I was pregnant and returning from ML).
I think that the biggest thing that needs to change is my mindset about this. I think that a lot of what she does is done to wind me up, and it works.
How can I disengage?