Travel during valid H1B to H4 EAD COS processing

We just got to know that my wife may have to travel to UK around end of May time frame. We would like to understand the implications if her H4 and H4EAD applications is processed and approved either before or during her stay in the UK. Specifically, we are interested in knowing if she can re-enter the United States using her current H1B visa, which remains valid until approximately August or September?
Please help us understand the scenarios where her H4 may/maynot be filed for future date.

Travel While H4 EAD is Pending is allowed. Pending H4 extension or COS may be abandoned, H4 EAD may receive RFE to prove H4 status by sending new i94.