some cats shed their winter fur but if she is an indoor cat she wouldn't grow one LOL. What colour is she and is there much that brushes out when you are brushing her?
She probably drops fur like we do with our hair- so few it isn't noticeable.
Some cats are like this, consider yourself lucky! Nothing like having a white or black cat on your lap while wearing the opposite colour.
Maybe in her lineage she has a bit of one or two of these breeds of cat in her DNA. Two cat breeds are often touted as shedding a minimal amount. The Cornish Rex cat has short, curly fur that lies close to its body. The Devon Rex is similar and has curly fur that can be in a very thin coat across the cat's body. Both of these cats may shed less noticeably due to their short, fine fur.