Not that I, uh, got suckered into buying one or anything, but they're pretty useless for larger dogs because they lack the power needed to grind thicker nails. They come to a complete stop when a bigger dog's claw comes in contact with the drum part. It might not be bad though as an introduction to a dremel-like tool and could possibly be more effective on a puppy's nails than it was on my dogs. (Not that I got roped roped into buying one, I swear!) They do make some noise but nothing close to an actual dremel.
If you aren't comfortable with the nail trimming thing this go around, then take her to a groomer and watch what he/she does but I really recommend you let your dog get used to you handling her paws and nails. This way you can easily do her nail trimming yourself which saves money and will potentially be less stressful to your pup since she sounds a bit fearful of things in general.
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