She sounds right on target and is doing a lot already. She's verbal with her voice AND she's signing. She's at a prime age and readiness for learning baby signing (you know this since she's waving hello and good-bye, etc). Simple commands at this age are difficult and I think you're overshooting a bit. With our eldest children we focus everything we have on them and they're very often more verbal, earlier with speech, crawling, walking, being social, learning to play with certain toys, etc. Then when a sibling comes along and there's split attention and we forget that they're individuals that grow and learn at their own pace, we compare them and worry that one isn't doing something by the same time the other one did.
As another poster said, your 10 month old is not only developing at her own pace but she's observing everything. She has an older sister as her role model.
I didn't see that as much with my 2nd daughter due to developmental delays so we had to learn quickly not to compare them especially since she had a lot of regressions (thank you, Autism, even though we didn't know it was ASD until she was a preschooler) but with my 3rd daughter she had TWO older sisters to observe. She did some things early and some things later because she wanted to perfect things in her head first. She's almost 9 and she still does this.
Plus... over children aren't trained monkeys. :-) They're tiny people that won't necessarily perform on command. She might not understand some of the words you're using yet even though she understands a lot. She's still learning the language, so cut her a break. ;-)