I don't have an option to make life fruit pie, but that could be because I don't have any lifefruit. I will have to download BB and do some more testing. I only have the basegame installed, with this set and the berry set installed. so far, without checking on lifefruit, no reverse aging is occuring. Be back again in a few.
EDIT: I played Josephine Coastal in BB, got her cooking up to level 9 (required to make Lifefruit Pie) and when she ate a slice of pie it lowered her age by one day. I think it may be ok, though, because the option to make the pie doesn't exist unless you have lifefruit in your inventory or refrigerator. So, since there's a rule about not having special seeds or lifefruit/deathflowers in our inventory, I think we should be okay to allow it...pretty please, with a cherry cobbler on top?