Leg humping

my girlfriend is a black beautiful bbw woman and im a white man. we are best freinds and lovers. the first time we had sex she came out in this short night gown shirt displaying her legs. i thought she had the most sexy legs i had ever seen. so i asked her if i could love on her legs and she didnt know what i wanted too do but said it was ok! so i got on my knees behind her and sandwhiched her legs around my penis and dry humped her legs until i orgasomed all over her legs and shoes. now she knows i love it she always teases me with her legs showing them too me and says she liked it too, and i love doing it. is this normal?