I DISCOVERED THAT MY GF HAS THIS, BUT I NEED HELP

i'm (19M) in a relationship with my gf (18F) since 2 years, we always been a bit playful when going to the bedroom, but never done this fetish ever, but when we hang out yesterday she ripped a pretty big fart, and she said "imagine if it was on your face", laughing, and without thinking i said "i wish it too" so we remained silent for a bit and later kissed, then she told me that i could come over today (in about 5hs from now), i'm SOO nervous because she said she wants to do "something different" and she has "prepared a cake for me".

this is a dream but now i'm very very very nervous and i don't really know what to do, any tips? i will post how it goes