"my mother died a few years ago".
So what has happened in the intervening period? - who was appointed executor of your late mother's estate? (either you or your sister, probably) - was probate obtained giving the executor power to deal with the assets left by your mother?
This questions creates more questions than it asks, but the straight answer to the question you did ask is that the property is left to whowever it was willed in the last will.
Tell us the answers to the questions above and we will make some suggestions on what you might do next.