[souffle]

You should check her teeth are OK But try and do this yourself. Your vet does not sound the best at handling. If she is having trouble eating then you could also soak some of her regular mix to soften it a bit. You have to watch they don't store the wet stuff as it can make them ill if it goes off in the store.
Strokes can affect them in the way you describe so it could be that. If she is getting fluid from the foods that is good too. Watch outthat she is weeing and pooing as sometimes a stroke can affect digestive function. Watch for bloating or straining. If you do take her back I'd insist you handle her. The teeth should be short at the top and the bottom two teeth should be aligned and not splayed but they are fairly long and as long as they appear even and not jutting in to the roof of the mouth they are likely OK.
Keep feeding the hard food though so they are still grinding the teeth together to keep them worn to correct length.
I hope she rallies round for you.