What do you mean she "singed over" the house? Did she deed the home to your sister? If she did, what kind of ownership did she give her: 100%; was it joint tenants with rights of survivorship; was it tenants in common?
You use the term "beneficiary" - was this done through a trust?
If you sister is now the sole owner listed on the deed, the property may belong 100% to her now and she may be the only one who can now change the ownership of the home (unless you can show that such change in ownership was made under duress or undue influence or that your mother lacked the capacity to do such a thing, etc.). You should speak to an attorney who practices real estate law in the state where the home is to see if: (a) the deed was properly recorded (if it was not, then the property's ownership may not have changed legally); (b) any undue influence, duress, capacity, etc. claims may be made; (c) see if there are other means available to you to have all children become owners upon you rmother's death or now.
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