A: Unless the interest is held in a trust, corporation, LLC, or other entity requiring both of their signatures, your wife can sign the lease for her interest without her sister's signature. If her sister doesn't sign, the oil company can force pool the sister's interest in a force pooling proceeding before the Oklahoma Corporation Commission. Sign the lease, take the bonus money and let the oil company worry about getting the sister's interest under lease.
A: Leases can be bought and sold many times before and after there is production so it is not uncommon for the operator of the well not to be the original lessee. Royalties are suspended because the operator can not mineral owner the owner or there is an issue with the title of the property that prevents the oil company from paying proceeds. Often times there are missing probates or other issues with the title. You should ask the companies the reason for the monies being suspended and also what needs to be done to correct the issue. You may need an attorney to help you correct any defects. You should also check with the state unclaimed property division to make sure no moneys have been paid over to the state.
A: She should consult with an estate planning/ real property attorney. It is likely you will need to obtain deeds from the children of her siblings, file one or more probate cases, a quiet title suit or some other action to resolve the issues created by the length of time since her father's death. Her making a will does not protect the property from the claims of the other parties, it merely directs how her interest in the property will be transferred upon her death.