Roist - my understanding is that you sometimes feel your wife meddles when you are handling situations with your kids and then she inadvertently undermines you? Is that correct?
If so, (sheepish look) I have been guilty of doing the same to my h. One thing my h started to do was to tell me beforehand that he was going to handle x situation with the kids and he'd appreciate it if I left him to it. That helped me not to interfere as when I heard any commotion, I was expecting it/prepared for it and did not feel that knee jerk reaction to meddle.
Prior to this, if I did interrupt, h was polite but firm in telling me he was handling it and would wait until I left to resume. That worked, too.
For me, as I always handled the majority of issues, I think it was a habit (albeit an annoying one).
Perhaps try giving her a heads up even if it's a last minute situation?
Me 41, H 47, M 15 yrs, S11, S13 BD 1: 11/4/14 we work on it; really I pretzel myself BD 2: 3/31/15 H goes down to "dorm room" 8/15: H back to MBR 10/15: H back in dorm room 1/18: H files, now divorced