Animecrazy.net
that's episode 51 watch it here http://narutovideoseries.com/naruto-shippuuden-51-reunion/
There is no episode 875 in the Naruto series .
Episode 90 You Can Watch It Naruto-tv.com
You can watch it at either www.animefreak.tv.com or www.narutoget.com
Animefuel.com
At chrunchyroll.com
tailedfox.com
narutoget.com
Animecrazy.net
probably on youtube, just search NARUTO LOST EPISODE and it might show up.
She comes in Naruto episode 110(not Shippuden). The name of the episode is: Formation! The Sasuke Retrieval Squad! You can watch it on narutoget.com.