What can I do to protect my interest in an estate inheritance ?

Mother passed without a will, no executor or probate at this point. Sister and I are only children no spouse. Sister secretly obtained $8k cash from mother's valuables at hospital when she passed and has not come forth with those proceeds, I obtained documentation of the release from the hospital to my sister. My mother owned a house (outright), there were back taxes totaling $3k and IRS taxes totaling approx. $2k. I'm fearful that the county or irs will impose tax liens or force tax sale of the property. Is there anything I can do, is this legal ?