Lol, Nicola, I'm sure you aren't toxic. H's XW really is (though it took me a long time to believe it). She would never be able to look at herself the way people do here.
"I guess my question is really, why do they put up with it?"
OK, but you are still assuming H's actions are due to OW being controlling. It comforts you in some way to think that. But, you actually have no idea if that is the case unless H has told you that OW is very controlling or you have seen/heard OW "make" H limit his contact with you. You would like his changes to be due to her being controlling, but maybe they are just his changes that have nothing to with her. Maybe he thought the ride was fine because the kids are older and he always thought you were overprotective, but went along with you to keep the peace. Who knows?
Really, my point is that there is too much explaining away a WAH's behavior by putting it on OWs. WAHs make their own choices for their own reasons. Your H may leave quickly when he is on his way to see OW (how do you know he is, BTW?) because he feels uncomfortable talking to you when he knows that his involvement with OW hurts you and he is on his way to do something that will hurt you. WHO KNOWS. But, obsessing about it and making OWs into evil, controlling b*tches to avoid confronting the truth about the WAH and the state of the M really is not helpful. I am not suggesting that you are doing it. Really. My comments are meant much more generally about something I see happening all too often.The problems between the LBS and the WAS are in the R between THEM. Truly. Making it about an OP feels better, but it is hugely counterproductive.
That being said, I agree that many GFs of WAHs are terribly insecure. XH came to visit me a couple of times for various reasons, and his GF called him, literally, like every 10 minutes. It was crazy. I am not sure why she was so insecure. I don't know what she knew about the circumstances when she started to see him (like we were still in MC). But, insecure she was. Did she feel threatened by me? WHO KNOWS? Maybe she didn't trust him in general. Maybe when she met him he was also seeing other women from the dating site he where he found her. Maybe he lied to her about stuff. WHO KNOWS?
It doesn't really matter. What an OW does or does not do is not going to determine whether a LTM in trouble is restored or not.
None of the constant wondering about the OW, her supposed power over an LBS, her motives, what she knows or doesn't know, and so on matters one bit. Because, the OW truly is not a member of the R that is in trouble, an R between WAH and LBW.
