H4 i539 transfer/ extension with multiple h1 transfer

My wife came to US on H4 when i was employed with Employer A. I got an offer from Employer B and Employer B filed H1 and H4 extension for both of us and got them approved. For some reasons, I didn’t join Employer B instead joined Employer C. Employer C filed H1 transfer and got it approved. My question is:

Is the H4 extension filed by Employer B still valid or Employer C need to file it?