Does Morgana have feelings for Merlin?

This of course is the beginning of their relationship, and when she subconsciously realizes that Merlin is one of the only people she can truly trust. His act of helping her meant so much to her that she actually was the first person to jump to the opportunity of helping Merlin protect his mother and village.

Why did Morgana turn on Arthur?

Morgana turned on him because she felt like she had to in order to survive—in order to distance herself from how much he had hurt her. Her heart was broken.