She wasn't rejected, at least not in Samantha's view, and that's not how it'll be reported either. She specifically walked the girl away offering to help her find a coven, having told her that she could apply to join Samantha's coven if she wanted. As far as she can tell, Lydia expected everything to be handed to her on a plate just because she talked to Samantha, and she shakes her head as she watches Lydia walk off. That's not how the world works and Lydia will have to learn that fast if she hasn't already.