Could you please clarify as to why you cannot use the "Lost Password" feature? Was the email account deleted, or perhaps it cannot be accessed? If the system itself isn't working, it should be bug-based. However, we need to know if the problem is on your end or SWC's end.
So you used the Lost Password feature on your other - sorry, your sister's - account, because you (she?) forgot the password. Then you deleted the e-mail that it sent to her address for her account... and you can't simply wait another 24hrs to use Lost Password again so you - sorry, she - can access your other - sorry, her - account.