L2 to h1b cos issue - urgent

My wife is on L2 with EAD working for company A. Company B had filed her H1B with change of status and it was approved a week back but the approval notice is not in her hand to see if CoS was approved. Now she does not want to join company B & wants to continue with her L2. I hear that her status automatically changes from L2 to H1b from October 1.

A. Does she have to leave US before or on sep 30 & return in October to retain her L2? Or

B. Can she wait till October 1st to see if her status has changed, if changed, leave immediately & return on L2?

C. If she does option B, will her job with company A & EAD become invalid if the status gets changed to H1B since she will be leaving US after October 1 & returning on L2?

I does not have much time. Any help in this regard will help us.

Thanks in advance.

Best regards