While only vaguely implied in the film itself, one must remember the time period and setting at which The Princess And The Frog takes place. Tiana is still going to be plagued by very overt racism, systematic oppression, rape, murder at the hands of the KKK, and pretty much many horrors for many more decades. America wasn't a friendly place at that time for a "woman of her background."
A bit meta, but Tiana was also, in early scripts and concept art, essentially a chamber maid of Charlotte, not a restaurant worker. Let that sink in. Disney originally wanted their first Afro-American princess....to be a slave. To make matters worse, her name wasn't the rather beautiful Tiana. It was "Maddy", a classical slave name. Luckily a brief outrage from a leaked early script made Disney back away from all these things.