The IRS should be using your 2019 tax return to determine whether or not you are eligible for the stimulus payment. It should not matter that your mother has not filed yet.
It can take the IRS several weeks to post the results of your tax return to the stimulus payment portal, so they just may not have posted it yet.
If you don't get the payment this year, you can claim it on your 2020 tax return when you file in early 2021. The payment is actually an advance on a 2020 credit.
You can continue to track the status at this portal: Get My Payment
See these Q&As for more info: Get My Payment Frequently Asked Questions | Internal Revenue Service
Economic Impact Payment Information Center | Internal Revenue Service
