First of all, it mentions that Yuko watch Prudence, managing the restaurant. The catch here, is that, there's no Pancakeria game where Yuko is a customers.
Secondly, she can be seen with a cup of tea in her Flipdeck. Tea is a drink available only in Pancakeria games, which, as mentioned before, doesn't have Yuko as a customer.
And finally, it mentions about her living in Tastyville and running the Lovely Leftovers, and a few years later, we have Pizzeria Deluxe.
What if there's an ARG inside her Flipdeck that's hidden, and if anyone could crack it, they would get the release date of Pancakeria Deluxe?