That's why we have something called separate characters.
We share only the gold. Of which we have plenty.

We play on each other's account from time to time but never do anything without consulting the other. ^.^
Now about the ''Disposing'' part.
My advice is to attack her from behind and put her in the sleeper hold until she passes out, then drag her to the bathroom and chop her up in pieces. Then place the remaining body parts in separate bags and put them inside you're trunk. Then at midnight drive somewhere really,really far away and find a remote part of no-mandsland and bury the bags containing the parts deep inside the ground. And also don't forget to clean you're car thoroughly while keeping a very sharp eye to the little details. ( This must be done the same night with as little noise and people around as possible )
Then report her missing after 24 hours,and from there...Later when you're at the station you say she told you that she went out for a walk in the cool evening breeze and that she would be back briefly.
After that play innocent. Still believing in the fact that one day you're beloved wife will return.
Just my 2 cents though.