If this issue ever becomes litigated, I think you would propound discovery on the biomom, asking for all relevant communications (mail, email, phone, etc.) that relate to the proposed relocation, and the timing thereof.
When biomom responds to the discovery, she will either produce all the information as required by civil procedure, or she will not. If she produces it all, then you have your ammunition there. If she fails to produce it all, then you can prove she has not complied with discovery.
