@db I would seriously look into getting your house blessed if this is happening. I know the Orthodox do it and I believe the Catholics do as well. You can always bless it yourself, do regular prayers and make the sign of the cross under doorways, but ymmv

The fact you can't stop thinking about her means you're more likely dealing with an egregoric demon entity than any ghostly spirit. They latch on to the residual soul left in places by the departed and spread fear. They're rarely physically harmful like in the movies but you'll be uneasy and restless until you spiritually cleanse the place.