Crating isn't cruel unless you have your dog living in the crate 24 hours a day. At 6 months of age, there is a ton of stuff in your house for her to get into. Cleaning supplies, power cords, t.v. remotes, socks - all are things that can be interestng to a bored puppy.
Crate training may come in very handy when your dog is older. If your dog has to travel on a plane, spend the night at the vet or anything of that nature - it is much better to have the dog already crate trained.