She isn't in Meereen. The final chapter of ADwD ends with her entering the captivity of the Dothraki. She will definitely be going to Vaes Dothrak, it's more about how she'll extricate herself from the dosh khaleen, if they even take her. She might try to be fireproof again, and GRRM has said she's not. I think it's likely that Drogon will rescue her, but he's had her on the pay-no-mind list many a time before, so while there will be a deus ex dracone, if you will, I doubt it will be immediate.

Tyrion is just outside of Meereen, but that doesn't mean Daenerys is likely to return there for quite some time. She won't be in control of her own movements, Hizdahr is no motivation to return, and as far as she knows, the city is at peace.