Maybe she borrowed some concepts. Or it also happens sometimes that you make up similar concepts found in philosophies and religions yourself accidentally( happened to me a few times, that was funny when I realized it
From your description it seems that Summer and Lewis are very similar in these things. Though it seems to me that Summer brings this need for validation a bit too far in that she never seems satisfied with her work as much as she should be. She always got a lot of compliment from Whedon and Josh Friedman let alone an army of fans and even critics but she just never believed it . I'm always heartbroken when she mentions that she didn't even want to try Serenity and Cameron
I think too that she is an incredibly intelligent person, her work and even her interviews always make me believe that. I always wondered from where did she get the inspiration to portray so many different kind of persons in such a deep and believable way, maybe its really that she observes and understands every people around her very deeply which knowledge she uses for acting. Understanding people so much would be an impressive feat in itself, mimicking it so perfectly on the top of that is just amazing. Summer is fantastic!
My heart bleeds because she is not more mainstream. Wasting such an incredible person is a terrible loss for all humanity and shows how much our cultural life degraded in the past century.