I think this is better. 엄마는(or 가) 그늘에 앉고 싶어해요.
What's the difference between 싶어요 and 싶어해요?
They explained this in the Verbs 2 tips and notes (which can be found on the mobile or desktop website) but basically you use ~고 싶다 when talking about yourself or asking a question but you use ~고 싶어하다 when talking about a third person.
I guess she is emo.