I'm thinking of falling in love with a very close friend
What makes you want to enter a romantic relationship with one of your friends?
I want it to go public and then get married.
I can understand your feelings about this. If this is something she wants too then you should go for it.
See, she's not just stuck up and selfish. She might have feelings for me, too.
Well, if you actually care and would like to one day marry this friend then there is no harm in asking them out. I hope the best in your endeavors!