Is my house haunted.

you just answered this lil girl's question who said she heard a child crying and you said it's all in her mind :p and you're freaking out because your light went on and off? lol don't worry even if there's something there don't freak out. you should start freaking out if weird things happen before you go to sleep or when you're alone.

It could well be a ghost.

Sprinkle some pills on the floor before bedtime and if they're gone in the morning, you're definitely in the grip of a Pacman manifestation. If so, seek the help of an exorcist IMMEDIATELY!

Theres always the posibility. Sorry i cant say yes or no. I live in a haunted house and alot of stuff goes on. More than lights going off. Try getting info about the house and land. Might help and make u and ur sister more at peace.

Ghosts don't exist, don't worry!!

Even if your house were haunted, what's the problem about that?
You should fear the living not the dead.

Was she drunk?

there is no such things

I can't really picture how your house looks like.
But one thing for sure, if your house is haunted, it won't be happening a month apart. If anything is roaming your house, it should be happening frequently cos its always there everyday.
Furthermore, why is it only your sister notice such peculiar things. Why not your parents or yourself?
I trust that you have been living in that house for ages, why only now? A house does not get haunted over night for no apparent reason.
Alot of times when things we can't explain, we always conveniently claim it to be by some unknown forces. Thats whats happening in religions, aliens, the universe.