So she could easily be taking 200mg three times a day. I'd probably try 150 but that means splitting capsules. I used to get the 600mg tablets instead, and use a pill cutter to divide them into 4 150mg pieces. Easier than capsules. But eventually had to move Leo to 200mg 3x. I used trocoxil too for a bit but eventually didn't see too much difference so just give metacam or tramadol on scratchy days (eg weather change days).
Start gabapentin at 10-20mg/kg orally 2-3 times daily (typically a 8-12kg CKCS would be started on 100mg capsule twice daily) with or without NSAIDS