Cookie Needs Surgery

I took Cookie to the vet after noticing some strange behavior and what I expected to be a simple bladder infection ended up being very large stones in her bladder which are preventing her from urinating properly. Without the surgery, it can be fatal.
My initial plan was to do the surgery in a few months after I was able to save up the money but her Vet expressed his concern with waiting that long given the size and number of stones seen on the x-ray.
I know she's "just a dog" but to me, she's family and has been a constant companion for the last six years.
Any help will be greatly appreciated.