Nami does
Luffy can be a baka and needs someone to guide him

D) who better than the navigator
If you exclude the obvious (dreams, nakama, family) both of their fav thing is food believe it or not

Nami loves money and Luffy is gonna be the PK (''the man who has everything'') and will at the end have the highest bounty hence will be the person worth the most
She gets to hold his hat, which in any other context would be meaningless but the hat in OP is the object with most symbolic meaning (colorspreads)
She was the only one of the SHs who appears at the beginning of OP Romance dawn right there next to luffy and shanks and a version of her is also in the previous two versions of RD
she might hit him but when they talk seriously they seem to understand each other perfectly
Nami looks kinda like rogue (dont really know why I put this in here, but still)
also there are a lot of little moments throughout the series
also the only movie Oda actually wrote (SW) is LuNa heavy XD
... one could go on but you get the gist
and why would Boa really fit shes over a decade older, shes two heads larger, ... and to others than luffy she behaves like a stuck up chearleader who thinks shes above everyone else (theres also the animal kicking lol)
the arguments going for her a shes hot, shes an empress and she loves luffy (mostly because she doesnt know any other man), if you look at those 3 Vivi would be a better match shes a princess (future queen), shes hot and I dare say she cares about luffy more than Boa