What is "Qulle une belle femme" not accepted?
i have this question as well, why is there no article in this sentence?
You don't need an article because there already is a determiner: the exclamative adjective "quelle".
I am puzzled by "quelle" that I associate with "which" turning into "what a."
"Quel, quelle, quels, quelles" can be found in two types of sentences: questions or exclamations.
Quelle robe mets-tu ? = Which dress are you putting on?
Quelle belle robe ! = What a beautiful dress!
That's where you hit the language barrier. It makes perfect sense in Swedish, actually
why doesn't beau work? Is it masculine?
Yes, "beau" is the masculine form, and it becomes "bel" if the next masculine word starts with a vowel sound: