You can discharge disabled employee if there’s no way to know when she’ll return

Employers don’t have to provide a disabled employee with an indefinite leave of absence when the employee has a medical emergency and doesn’t know how long it will take to return to work. As long as the employee isn’t covered by the FMLA (in which case, she would be entitled to 12 unpaid weeks of leave), you can terminate her without violating the ADA.