Unlike humans, animals don't have the brain function it takes to "want" or "not want" a litter. It instinct, like eating or drinking. Perception of cuteness is strictly primate, so they take care of litters as a sense of duty more than a sense of motherly desire that humans have.
There is way more than enough unwanted and homeless bunnies in the world. Unless I was heavily involved with showing, or an uncommon breed, I couldn't justify breeding. Therefore, I would spay.
And spaying changes behavior for the better! She's a baby now, and probably friendly and sweet. Around 5 months the hormones will start kicking in and she will have accidents, can become aggressive and territorial, can have false pregnancies, and has an outrageously high chance of developing painful and fatal cancer.
Spaying means you'll get to keep your sweet little girl's personality!