How much does the second wife of the deceased man inherit, and what is her legal and lawful share of the inheritance?

There is no inheritance between two wives, as there is no cause for inheritance between them. Rather, a wife inherits from her husband, and she receives one-eighth (of his estate) if he has a lineal descendant, as Allah Almighty says: "But if you have a child, then for them [the wives] is one eighth of what you leave, after any bequest you [may have] made or debt." If the second wife dies, her share passes to her heirs. The determination of heirs and their shares is based on Islamic law, not on secular law.