The short answer is yes, but whether she is successful or not depends a lot on the judge.
There needs to be "change of circumstances" but depending on the judge, that definition will vary. Ex took me back to court less than 2 years after our divorce - his change of circumstance? Marrying the OW. 😳
My lawyer didn't think the motion would even be entertained since he said usually that does not qualify. But my judge was new to the bench and let the hearing happen. 10 months and $15,000 in legal fees later, his motion to modify was settled.
(I agreed to some, but not all, his requests. He refused to budge on anything, so everything to had to go to the judge).
I know what you mean by ticking time bomb. I can't imagine I will make it until my youngest turns 18 without him taking me back to court.