Looks like she needs to go up to 6.5U tomorrow.
It's a pity your vet is giving you such a hard time about insulin. I hope that resolves soon. You might also want to keep an eye on the Supply Closet for anyone selling or donating insulin glargine:
https://www.felinediabetes.com/FDMB/forums/supply-closet-for-sale-or-free.15/