Oh boy, that's a toughie, Katherine. I hate to be a "me, too" but I think a second opinion is in order. I will say, though, that since you've ruled out surgery and you're leery about leaving Sydney at the vet's and stressing her out, the second option appears to be the most viable. My Creamsicle is on Prednisolone which does not cure her allergies, only manages them, but this is the option I've chosen. Granted, allergies and cancer certainly don't compare in severity but I'm sure you understand my comparison. Good luck, honey. You've done a great job so far and no doubt you'll continue to do so. Gentle pets to your sweet Sydney and (((HUGS))) to you.