If your MIL has an IRA, try to keep her from withdrawing more than the MRD (Minimum Required Distribution). Also, make sure that she has assigned beneficiary(ies) on the account.

Reason:
When MIL dies, your DW will probably inherit at least part of her mother's IRA. This IRA should NOT be rolled over into DW's IRA; that would "blow up" both of the IRAs.

Instead, have the inherited IRA retitled "Inherited IRA of Mother; Beneficiary account for DW." Then, your DW can keep the money in the IRA for the rest of her own life, withdrawing an annual MRD that is based on her (much younger) lifetime. That is, the fraction that must be withdrawn (and taxed) annually is much lower than her mother's. This can defer taxes for decades, giving opportunity for greater growth.

Wendy