When is it safe?

My mom has the flu or something like it- aches, fever, cough, the whole nine yards.  It started Wednesday evening, she spent all day in bed Thursday, Friday and yesterday.  Last night, she said that she thinks she's on the mend and we can still get together on Tuesday for Christmas.  In my head, I immediately thought no way in the world.  I said to her to see how she feels today and tomorrow before deciding.  I hope that she decides on her own to cancel or postpone our family gathering, so I don't have to be the bad guy.  But, I don't plan to bring LO around anyone that has been sick.  LO turned one year old this week and was a 27 weeker.  She's had Synagis (gets another dose on the 28th) and flu shots.

So, my question is when would it be safe to get together with my mom?  Three days after her symptoms are gone?  Three days after the fever ends?  What's your guideline?  I plan to call the pedi's office tomorrow, but I always feel like they are far less cautious than I. 

Thanks.