How common is cowgirling?

I've had a few metas try to cowgirl me out in the last few years. Hadn't encountered it before that and I didn't even know there was a name for it until I came on here. Have I just been unlucky or is this more common than I realised?

I'm thinking that it's some kind of mono thinking that feels you have to edge a partner out to make room?

How do you address it with a partner when you see it coming? One partner believed me, another didn't and ironically it was me raising it that finished things between us.

Edited to add:

Think I'm using the wrong term. When a new meta tries to push you out so they can take your place. Anyone else come across this?