When you approach on line portal, think and understand the limitations of advises sought through portal.
1)Your query involves process involved with three insurance companies and taxation.
2)First obtain sufficient number of original death certificates, copies of medical reports if any disclosing reasons of death, take sufficient number of photo identities copies of nominee., with original, visit insurance company , take individual original policies fill the prescribed form of claim and obtain acknowledgment.
Wait for a month or two enabling insurance companies to settle the claim.
If any taxation is there, the insurance company deducts TDS depending on the claim amount and generally it can not be done.
First let the claims be settled for all cases, and then consult any chartered accountant, to know as to how to avoid tax, if any due through investment in approved securities.
(If she is having children, without information and knowledge do not take initiative and lead without some other's assistance, as this may cause misunderstand in any financial matters)