My sister has made me mad so many times by not saying or doing something alone with me but then goes and says it to me in front of my parents, and I have been getting in trouble for it.
One word that might be suitable is fickle:
It shall be fickle, false and full of fraud,
Bud and be blasted in a breathing-while;
The bottom poison, and the top o'erstraw'd
With sweets that shall the truest sight beguile:
The strongest body shall it make most weak,
Strike the wise dumb and teach the fool to speak.
hypocrite might be the word you are looking for. Please have a look at the definition here