An employer terminating participation in a MEP or PEP does not constitute a distributable event under the 401(k) distribution rules -- no employee has terminated employment with the employer, and the plan, itself is not terminated.
The departing employer should get a spin-off of the plan benefits from the first MEP (no, this is ot "automatic"), and then merge that into the MEP with the 2nd group ... or she can put the spinoff into a new 401(k) plan sponsored by her corporation, and then terminate that plan. This is probably one of the biggest disadvantages of MEP/PEPs -- the exit strategy is not a cakewalk.