Only if the girl lives in a vacuum, with no other influences. If she has a family and friends, goes to church and school, competes in sports or learns to play an instrument, the chances are she'll have get idea that life has ups and downs, and achievements usually require effort, before she reaches adulthood.
The real risk of producing children with unrealistic expectations arises when adults insulate children from the realities of life: ban games or contests because everyone can't win at everything; fight about grades, instead of letting children get the marks their work deserves; argue with coaches or umpires, instead of letting children learn that sometimes life is (or just seems) unfair, and so on.
As long as she knows she’s loved and valued by her family and they’ll be there for her, then she can handle reality just fine.
Again, if you look at these stories, awful things happen! I mean- death of a parent, poison, rotten step parents, being throw out of your home, being sent to live with strangers, a monster at that!
Even in the face of all this bad stuff, the princesses don’t loose their core values. (and we ALL want a happily ever after— even at 50)