ok checking to see if a glider is dehydrated is super easy.
Gently, at the middle of her back put your thumb on one side of her spine and your forefinger on the other side and pinch her skin. Not the spine, just the skin. if the skin stays up like a pitched tent then she is dehydrated, if the skin snaps right back to normal quickly she is not dehydrated.
The metacam dose is .03 to .06 which is kind of unusual that they gave you two different doses.
For her weight the dose should actually be .07 i'm NOT saying to up her to dose, follow the vets dose!!
What i am saying is, it's a smaller dose of a diluted pain med, you should be ok giving her two doses in one day to get her onto the med schedule you want her on at night without worrying she got to much. i would wait till closer to 1 am to give it to her though so it's closer to the 12 hour it's usually given at.
i'm trying to word this carefully so you receive it the way i need you too.
Two months may seem like a long time to you, but really it's not and they will both be ok. i've had gliders separated that long before for medical reasons.
Keeping them separated is what is best for her to ensure she fully heals or heals as much as she can without making the injury worse. So please do not feel rushed to get them back together.
There are things you can do to make it easier on them, like swap fleece so they still have each others scent regularly and will continue to smell like each other.
there are bonding buddies you can get for them that are glider safe and about the same size as a glider so they have something to snuggle with. They are only like 10 bucks a piece https://www.facebook.com/CreatedMoments/
These are not toys, so she can have one in her hospital bin to keep her company. They are made with fleece so you can let them each have one for a few days, then swap the buddies like scent swapping you just rotate them back n forth.
Spend more time with him since you can't really handle her while she is recovering. She isn't going to WANT you to handle her anyways and needs as much rest as she can get, so that means you can focus a little more on the cage mate
change up his cage a little, give him new toys to focus on when he seems overly stressed at night. They don't have to be expensive toys, try easter eggs, curly straws pingpong balls ... things you can easily swap out and change up.