She's a great champ. Ranged silence, good aoe damage, armor buff with a heal component and full team heal as well. To be able to take advantage of the aoe you do want to be very tanky though, and her lack of CC makes Rylai pretty much staple/necessary.
As far as sending her bot and nowhere else, I think she could do well top. She's very sustainable and her spammable aoe means that as long as she's alive no one is capping the tower. With the slow from Rylai's and her silence, she can kite people for a very long time as well, meaning there's plenty of time for reinforcement to come, if she can't outright kill the target herself.