Friends Inconsistencies....

Ok, so I was recently re-watching all the Friends Thanksgiving episodes.

On the fourth season of Friends, Phoebe mentions she needs to call her mom to ask her a left-handed cooking question.  Now, correct me if I'm wrong, but Phoebe's mom is dead and has been the entire series.

I tried to google this issue.  No one seemed to fully address this issue.  There are some blogs out there that seem to have a problem with the inconsistency about whether or not the tv remains on consistently throughout the scene, but no one seems to address the bigger issue.  Does Phoebe mean her step-mom?  Does she have a step-mom that's still around?  Why doesn't she say 'step-mom' then?

Has ANYONE else ever caught this?  Does anyone else have a problem with this?