Shiro-chan says "あいちゃんたち" which literally means "Ai-chan and the others" (たち is a pluralizing suffix). I translated it as "Ai-chan and her sister" but feel free to change it.
Ai-chan, I hope you enjoy this...Shiro-chan?Is she sleeping...?I made a prayerA prayer?"May Ai-chan and her sister--not be lonely"...