Employer coverage lapse, secondary coverage

Story: My wife's small employer forgot to pay her bills and they cancelled the plan (unbeknownst to the employees). There has been a lapse since 12/31 during which time my wife (active BC treatment) has racked over $100k in claims. Luckily I've able to add her to my insurance retroactively but her employer is asking her to get on a new plan starting 2/15. Question: my OOP max is lower and so I'm concerned if she's on both plans, my OOP max will trigger for the lapse and then her "new" plan would reset the clock as her primary insurance (and mine would become secondary). Am I thinking about this correctly? tldr: wife lost coverage due to employer. my plan will cover retroactively, should she stay on that alone or also sign up for employers new coverage and have both.