Again, just my cat lover lay person opinion - I would try the Mirtazapine first and see what happens. If she improves on that just alone, all the better - less meds. Why give her the nausea and acid reflux since neither of those seem to be needed right now? If she starts eating more and she throws up food again, maybe then you would want to add them.
Edited: Just to throw out another thought - if you can, time permitting, what about trying to feed her smaller amounts more times in a day. So, if she eats 2 meals a day, give her the same overall amount you want her to eat, but make it 3-4 times a day?
Edited: Just to throw out another thought - if you can, time permitting, what about trying to feed her smaller amounts more times in a day. So, if she eats 2 meals a day, give her the same overall amount you want her to eat, but make it 3-4 times a day?