Britedark, you are not a terrible person!

Rose76 is right when suggesting "claim your space and own your space". Some people feel they have to hug and kiss everything that moves. It may be a need to be loved. Or, to make up for a lack of demonstrative love when they were younger.

In your situation, you are responsible for setting and reinforcing the boundaries. Unfortunately you will need large measures of perseverance and patience. You may also feel guilty as she's your sister. Suppose you could call it "tough love".

Not adding anything to the already excellent contributions, other than to wish you luck.