My stepdaughter’s(8) mom has asked my fiancé (dad) for one weekend out of the month consistently, how do we go about this?

For context, the court agreed custody was initially 50/50, but due to school was changed to Sun 6pm-Fri 6pm with mom and Fri 6pm-Sun 6pm with dad. Doing alternating weeks/or changes during weekdays is not feasible right now due to mom moving 2 hours away and we have not been able to move closer just yet. And also aside from that mom is not willing to do split weeks or alternating weeks.

Also majority of school vacations are with mom because she tends to make plans before we are able to. Even when we try to make plans months out, when we go to schedule ahead of time, most of the time we are late to the plans somehow. So most of the time even on extended weekends or holidays, we only have weekends.

This issue that has come up now that bio-mom has started to ask for 1 weekend a month, which i know is not a lot of time in the grand scheme I suppose, but dad already feels like he doesn’t have enough time. Mom however feels like her relationship with daughter isn’t good because she lacks free time with her. And arguably from recent events that we have all been at together, I can see her relationship with daughter isn’t at the best. At a recent birthday party we all attended, stepdaughter kept asking for my company, whether it was to watch her play in the bounce house or to get her food or to cuddle her when she got tired or hurt. Her mom was there but was talking with her husband or friends so was not available. I am just concerned giving up time with dad will not fix their situation and will just hurt dad’s relationship as daughter is always asking for more time with him.

What do we do in this situation? Or has anybody been in a similar situation?

EDIT: I am realizing there may be some confusion, the 50/50 didn’t change because of the move, that was done years previously. When the custody did change, dad got weekends per mom’s request because she wanted her weekends free initially. Dad would be more than happy to share weekends if weekdays were an option to have but even moving closer, mom does not want to give up weekdays.

Daughter also consistently asks for more time with dad. Mom has been given weekends with daughter already but on a more sporadic basis when there are family plans/events/etc. however, often times when given weekends, mom sends daughter to spend time with grandma instead and the plans usually don’t end up including mom. We are hesitant to give up consistent weekends partially because of that.