Dear friend,
If your mother's will states the you and your sister should split the house, it is the will that remains in effect whatever the circumstances. Your right over the split house remains. But Above this, you question is bit unclear and this does not pertain to your mother's finances but pertains to your mother's estate.
The best thing to do will to contact an Estate Law Attorney for this and he would be the best person to guide you.
I hope the above helps...
Regards,
Financial Advisor
Technical Analyst in Financial Markets -- Experience of more than 10 years in consulting