What is weird is why Ohm does not make this his priority. I mean, any decent man facing the same situation would…
AFAIK he is sure that Mark is his son. It is just us speculating about it. I'm just stating facts, he said that he will wait for her till the last minute.
We don't know the full story yet, and I think Mink is doing what she's doing not for comfortable situation. But yeah, whatever the reason, she betrayed Ohm.
Looks like you have already forgotten what happened in the beginning of the story. Ohm took the blame for Mink and ruined his life for her sake. And yet he found out that Mink and his son (as he thinks, maybe Mark is not his son though) are alive. What he supposed to do? Forget and give up on them and stick to Jay just because she supposed to be the FL? He can't give up on Mink unless she gives up on him.
We don't know the full story yet, and I think Mink is doing what she's doing not for comfortable situation. But yeah, whatever the reason, she betrayed Ohm.