Biggie, you can't help but be concerned about her, and it's admirable that you don't want her to feel guilty, but, the more you write back the guiltier she'll feel. I know that sounds strange, but it's true. She writes to see how you are, you respond, she thinks, oh, he still needs me, he still cares, oh that's so sad and it's my fault that he's hurting, got to fix it, send another email, etc. etc. it's a vicious circle. NC, it will take a while before she realizes that you are okay and are living your life, but she will get it eventually, although she'll probably never give up hope that you can still be friends. :)
Women, they're confusing aren't they? ;)