NJBYTCH - You're describing a very complex situation in terms of your family and the reaclimation of your sister into the household. These problems aren't limited to you or your sister, but extend to your parents as well (grandparent too for that matter) and the way everyone in the family relates to each other.
I see two issues that pop out immediately upon reading your vignette.
1. Freedom to Captivity
2. Boundaries
1. There's an old expression "After a taste of freedom captivity is no longer the same." Your sister had independance for a while she was free from the protective wing of your parents and on her own. Even if it was just for a short time, it's a huge adjustment to be back. Even if your parents leave her alone captivity, the fact that she's living in their home curtails her freedom. Her bitchyness (sp?) to you
may very well be displaced rage against her situation and resentment about having to be back in your parents home.
2. Boundaries. Clearly her behavior is inappropriate. Running to parents to "tattle" may be cute at 4 but at 13 and up it's just obnoxious. Your sister overstepped her boundaries when she did this. You should discuss with her the need for each of you to have your own space. Your business is your business - not hers.
Similarly, your parents exceeded improperly if they heeded your sister's revelation and chastized you for being on line.
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