Golden on gabapenten not eating and woozy

Hello everyone! I have a 9 almost 10 year old golden retriever. She was acting a little off a week ago so we brought her to the vet and they told us she has a pulled muscle from trying to jump through 3 feet of snow we have right now. They put her on one medication that worked well but caused her to get sick for 2 days straight. We called back and they put her on 300mg of gabapenten which we started 2 days ago.

Since she started taking the gabapenten she has been refusing a lot of food, she will eat some stuff but only laying down and when she wants to. She has been walking really wobbly and hasn't moved much, when she does her legs slip all over the uncarpeted floors.

How long will these side effects last for her and how can I help her feel better sooner? I know she's not young and unfortunately she may never fully recover (or she could) but I want to make sure she's both not in pain but also able to walk around and do what she wants to throughout the day too.