It appears authentic in the photo, but I'm no expert. There might be some info (date, director, animator, authenticity stamp, etc) on the cell itself. CAREFULLY look between the paper frame or take it to a animation cel dealer. DO NOT RIP OR DAMAGE THE CELL. Even if you just have the production company/distribution company name, that can tell you when the cell was made. For instance, if "Buena Vista" is on it or "RKO" is on it, that will give you a time-range for the cell. Look on the back - is there a dealer's label? Any info saying where it was bought or sold? Another thing, is it framed or just in a mat? Anything identifiable on the outside?
The character could be anything from Sleeping Beauty to Pocahontas. The outfit looks Elizabethan, the girl has dark hair, her eyes look blue, she seems scared or surprised, she looks like she might have a veil on - maybe she's getting married?
What it isn't:
Mulan(Hello, this one is in China - no "Rennaissance" or "Elizabethan" outfits
Robin Hood(no humans)
Fox & Hound(dress/animation style not right)
Pinocchio(style not right)
Jungle Book
anything PIXAR
Tarzan
almost anything with Mickey Mouse
almost anything with Pluto
Cinderella
What it might be:
Little Mermaid(clothing might not be quite right, cell looks too old?)
Sword in the Stone(are there even any women in this one?)
Pocahontas(cell too old?)
Sorry I couldn't be more help,
agnes!