Dog gabapentin vs Human gabapentin

I am 22. AFAB (Non-binary/trans). I am 190 lbs. I do not smoke or vape. I have ADHD and generalized anxiety disorder.

I currently am on gabapentin for anxiety and it helps calm my nervous system, for about a month. I am low on my doses. I have 100mg capsules. I take 1 at morning, one in the afternoon, and 3 for bedtime along with melatonin. I currently only have 6 left till Monday when it can be refilled. Is there any way to safely space this out?

Also my grandma suggested I could take some of her dog's gabapentin which is in bar/tablet(?) form. They're 600mg and could be easily broken in half- for bed. So I am not without for a whole day or two. Her dog had an accident which required surgery almost a year ago.

Would it be safe for me to take it? I am very skeptical when it comes to their advice and medicines in general. I don't believe them.