"Maybe you should for today."

Probably the best idea. But, this mermaid is most likely connected with that young girl more closely than she knows. It's what Gandalf assumes from what he has seen, and feel.

"But do not stay out of here definitely. I have a feeling this painting may be linked to you in ways we cannot see yet. Maybe as a part of your past, maybe of your futur, maybe something else altogether. For you to grow as a person, it can only be a good thing for you to find out and have answers."