I don't think that's how omnibreaker works.
Omnibreaker works by having a two skills that force doubles on either offense or defense + one that prevents follow-ups.
L!Hector can do that because he can double up on defense with VF on B and the QR seal thanks because his weapon has innate WF. Original Hector and B!Hector can also do that thanks to their weapons having QR (so they can run WF on B + the QR seal). B!Ephraim and Duma could also do something similar.
H!Myrrh, however can't, as her weapon only works on initiation. She could double up on offense with BF on B, but can't use WF then. She would need a WF seal for her to omnibreak on offense.