partner is entitle to get financial details. in your case your partner's wife has right to get details from the date when she came in partnership firm only because she is not bound to bear financial related liabilities beyond such date. though partnership firm has no legal entity but it can't affected by any changes in capacity of its partners.
She earned estate in your partnership so she has right to call accounts of the firm. If you feel that her conduct is not proper and against the interest of the firm then you have right to expel her.
under Section 33 A partner may be expelled from a firm by majority of the partners, save in the exercise in good faith or powers conferred by contract between the partners.
section 9 provides general duties of partners i.e. partners are bound to carry on the business of the firm to greatest common advantage, to be just and faithful to each other, and to render true accounts and full information of all things affecting the firm to any partner, his heir or legal representative.
so if you feel that a partner has no common advantage then it may form basis of expulsion.
Borne in mind after expulsion she has right to get account of firm from the date of her joining.