I don't know if CO has a "name change fee". Probably.

In the alternative, for a fee free option if another female wants to take the trip and could do it with just a carry on (or have their luggage checked in by someone else who might be going on this trip), that "other female" could print Mom's boarding pass and stick it in her pocket. She could then buy a daily lounge pass and ask for a gate pass in her own name, or could just ask for a gate pass to accompany someone to the gate (perhaps there is a child going on the trip, etc).

She clears security with the gate pass, then uses Mom's boarding pass to fly to and from Hawaii.

Mom's OnePass account could get suspended if they were caught, but the changes of getting caught are pretty low. I've never had my ID checked when boarding.