First of all, up to the date that ownership actually changes, whether that is through a sale or a foreclosure, the current owner/landlord has a right to collect the rent and keep it. Second of all, the owner also has a right to sell the property. And third, even if the owner IS in foreclosure, he could be trying to either modify the mortgage, which he is absolutely entitled to do, or short sell the property, which he is also entitled to do.
An awful lot of renters are under the mis-conception that if a landlord is in some stage of foreclosure that the tenant doesn't have to pay rent, or that the rent has to be paid to the bank. That is absolutely NOT the case, the owner is the owner and entitled to collect all rents until such time as ownership of the property actually changes.
If you are worried that your mother in law might have to move, contact an attorney or your State Department of Community Affairs and find out what your rights are, but in the meantime, continue to pay your rent as promised. Otherwise you stand to be evicted and that is not good for anybody.