The first thing is to determine if this is a shunt or MVD. A liver shunt can often be surgically repaired, and MVD can be managed through diet and supplements. Honestly, I'm surprised you said your vet is going ahead with the spay without further action. Denamarin or similar supplements can help reduce the liver values; adding Milk Thistle daily is also a good way to control ALT.
If there is a specialty vet near you, seek out an internist for further testing and to determine if it is a liver shunt. I personally know of a very sick one year old maltese/poodle mix years ago who we did not think would survive because the liver shunt had been untreated for months. After successful surgery, this little guy, Samson, lived another 12 or 13 years.
Good luck to you!
If there is a specialty vet near you, seek out an internist for further testing and to determine if it is a liver shunt. I personally know of a very sick one year old maltese/poodle mix years ago who we did not think would survive because the liver shunt had been untreated for months. After successful surgery, this little guy, Samson, lived another 12 or 13 years.
Good luck to you!