Could that mean that my mom is not getting an Employment Authorization but a Green Card if her status has not changed?

No the green card happens after an interview, usually. It is possible that the two applications are going to be processed a few days or even weeks apart. If you filed for their I-765, that is usually adjudicated first, before the interview for the actual green cards is set.

No. It just means that your mother's I-765 application hasn't been completely processed or approved yet. If more than 90 days have elapsed since the application was received by USCIS, she should call customer service at 800-375-5283 to inquire about the case.

Sometimes two cases filed at the same time Are not always processed at the same time. A few months ago I filed two applications same time. An American citizen son filed for his mom and his dad. We put both application in a single envelope with request not to separate the two cases. A few months later one parent got a work permit and the other one was approved for the same about 10 days later. One parent was scheduled for interview about four months after filing. She was approved for a green card on the interview day. It took 4 additional months for the other parent to be scheduled for his interview. We regularly file two applications at the same time if they involved one single petitioner. I would say about 90% of them are Kept together and the other 10% are being separated. I have not figure out an explanation. Your other parent should most likely get his or her work permit pretty soon. It usually takes an average of 2 to 3 months for work permit to be approved.

If both parents applications were sent at the same time, then, both applications should be processed at the same time, especially, if both cases have the same USC petitioner (you). Please confirm CIS has not requested additional evidence "RFE" from the parent whose EAD has not been issued and that it has not made a decision that the parent is not eligible to adjust in which case, no EAD will be issued. Make an Info Pass inquiry with your local CIS office. Occasionally, up to date information is not shown at the uscis web site.