Bertinelli wasn’t actually in negotiations, but she was up for the role

While IMDb makes it sound like Bertinelli was a shoo-in for the role and turned down the offer, that isn’t actually what happened. Producers hadn’t offered Bertinelli the role of Jamie, but she was up for the part. Bertinelli, like other actors, had auditioned for the job. She got close to nabbing it, but producers decided to go with Hunt instead. Teri Hatcher was also in the running.

https://www.cheatsheet.com/entertainment/did-valerie-bertinelli-almost-starred-in-mad-about-you.html/

Valerie might have been good in a different role on Mad About You. No way could she fill Helen Hunt's shoes though.

No way could she fill Helen Hunt's shoes though.

Valerie has said that exact same thing.