All of the above. Complete blood work including screening for TBD, "clean catch" urinalysis/culture, fecal exam, abdominal ultrasound, x-rays if something bone related is suspected, dental if maybe something in her mouth is bothering her, acupuncture, chiropractor, reiki, T-touch massage, whatever works., but not necessarily in that order except for the first three. I am sure that you can work with your Vet in a way that makes sense to get a diagnosis for what is going on with Ava. Perhaps a referral to a board certified internist?
I hope the dx is quick and easily resolved. Sending prayers for you and Ava.