From personal experience, there's a right time and a wrong time to feed a woman weed. If she's already horny, it will send her though the roof; if she's not, being stoned might make changing her emotions
more impossible ;-)
As for helping a woman horny, just walking trough the RLD might do the trick (
story). Even though I've heard it's a coin toss, the only time I went to Sameplace, it turned out to be a dud. The circular bar is nice nevertheless, and I find it worth a visit regardless. If your lady might like watching female strippers, there is
La Vie en Proost to set a mood; there I've witnessed some exceptionally hot lap dances from dancers I know with female clientele. (p.s. Avoid crowded weekends, respond with "maybe later" if solicited to buy Champagne, wait for a dancer to strip naked before engaging in a 20 euro lap-dance, or just buy yourself drinks and watch).
As for cake or smoking. Even few puffs of a good sativa might send her further than you want her to go. A half a piece (or a third of the strong cake from Paradox) is a good way to limit the effects to something sexually positive. The effect of a cake also slides in slowly; one or two cocktails usually goes good with that.
... Eric