My first stepfather purchased it for her prior to his passing. My recent stepfather's adult children are verbally abusive and make my mother nervous.
The stepdaughter smokes in the home although my mother has copd and is on oxygen 24/7 and does not want smoking in the home. Any time she attempts to express her wants the girl starts screaming at her.
I want to purchase the home so I can then evict the stepdaughter and give my mother some peace.
How long has stepdaughter been there and why? Has she paid rent? Utilities? I think getting SD evicted would be ur best bet. SDad owning half the house does not mean she has a right to live there and make Mom uncomfortable in her own home. SD is now an adult and needs to be on her own.
You would only be buying half the house unless stepdad is able to agree to the sale. Is he competent, if not does Mom have POA? Does the POA read she can sell as his rep if he is incompetent?
You may need a lawyer to sort this all out.
If she inherited as the sole heir after his death, then she can sell it. Check the deed; how is title vested (described)?
As to someone smoking in a house with oxygen, that's not only a big no-no, it's a recipe for disaster. Do these stepchildren live with your mother? If not, she has the right to ban them, especially if one refuses to stop smoking, which is not only dangerous but negatively impacts your mother's breathing ability.
In addition, someone who screams at an older person is not a desirable person to have in the house. Maybe she needs anger management counseling.
Your mother can evict this person but will probably have to go through legal proceedings to do so. Still, it can be done, and from what you write, SHOULD be done, ASAP, to protect your mother's health.