How do I handle this effectively?

For some unknown odd reason she is just plain jealous of you. Everything you've stated are pure signs of being jealous of another person. It also shows a sign of weakness & selfishness. You've given her absolutely NO reason to feel this way about you, this she's taken on herself for some unknown reason. Your parents never favored either one of you over the other, that can't be her reason! She also has an inferior complex about herself. ALL these things are of her own doing, you can take NO blame whatsoever for her personality traits. If this is the way she's going to continue to react to you, & I don't foresee it changing. I would instead just start to pull yourself away from her. If she doesn't choose to email you other than make the remarks she makes, I would stop emailing her altogether. See IF just maybe not hearing from you may start to make her think of how she's treated you all these yrs. growing up. Let her do some soul searching about herself. Let her see how it feels to be neglected. It just may be a good reason to finally bring things to the surface with her. You sure wouldn't be doing anything against her or anything hurting to her. Put this distance between the two of you, see if maybe in the long run it just may bring you closer & turn out to be a positive happening. Give her time & space & see how she reacts to you. I feel you have nothing to loose, possibly a lot to gain...the best to you, honey...:)