02-15-2010, 05:46 PM
Actually, you've gotten things a bit mixed. As long as both of you behave yourself; and she introduces herself as your sister and doesn't just start posting out of nowhere (that's when we think people are making multiple accounts, by the way) she should be fine.
However, if either one of you ends up being temp banned for breaking tons of rules, then the other will be banned as well. You should also make sure that you log out of your account before your sister goes on, as sharing accounts is against the rules and if she breaks rules on your account, could get you in trouble.