In the sign in for TalkTalk Mail (Click here), after entering the tiscali email address there's a Forgotten your Password? link. Select that and your wife will see options for receiving a password reset.
Please do try the Forgotten your Password option. If there's an alternate shown that she recognises from the hints, and has access to, then please reset the password.
If there's just the option of sending a reset to the same email address then that means your wife hasn't set up Reset details - an alternative email address and optionally a mobile number to receive a reset link or code.
If the self-help password change / recovery options aren't effective then I'll alert the TalkTalk Community team for you.
In the meantime, please update your Community Profile Personal Information (Click here) to include your wife's name, current contact 'phone numbers and address with postcode (location) then scroll down to Private notes and add the tiscali email address and Save changes.
The registration of the email address will need to be verified and when verified, new password Reset details will be set up and one of the TalkTalk team will call on the mobile to check security and let her know to go through the Password reset journey to set her new password.
No problem, just ask your wife to join the TalkTalk Community. Heads up that she'll need to register on Community with a different email address that she can access and use to verify Community membership.
Of course the same email address can then be offered as the alternative for Reset details to be set up so she'll always have a way of recovering access to TalkTalk Mail should she forget the password or in case the mailbox becomes suspended or blocked by the system security monitor if suspicious activity is detected.
Your wife will need to post asking for help. Obviously, I have to believe I'm speaking with your wife in order to pass security. Please ask her to sign in using the username you've setup for her and then I can send her the personal message for the security information.