Dear Jackie,

Love philter = love love potion (a redundancy, perhaps intentional from the calculating Ms. Stewart?)

Here's the bit from Bartleby:

VARIANT FORMS: also phil·tre
NOUN: 1. A love potion. 2. A magic potion or charm.
TRANSITIVE VERB: Inflected forms: phil·tered also phil·tred, phil·ter·ing, phil·tring, phil·ters, phil·tres
To enchant with or as if with a philter.
ETYMOLOGY: French philtre, from Old French, from Latin philtrum, from Greek philtron, from philein, to love, from philos, beloved, loving.

Best regards,
DubDub, who ain't found such a concoction -- yet!