How can I set my EB-5 visa interview in the U.S. since I cannot get back to my country because of Covid restrictions?

Once she arrives, you should be able to file an adjustment of status at USCIS.

Once your mom enters the U.S. as the principal, then you can file to adjust status here as a follow-to-join derivative provided you have maintained your student or other status.

If your mother has been approved, she should file the I-824 following to join for you. Also, if you do not, you might age out if past 21. If she has been approved, you can also try and file an adjustment based on proof of her approval although the I-824 is the preferred way from USCIS perspective.

You cannot do your NVC interview in the U.S. However, you can potentially file an adjustment of status application once your mother gets in as a conditional resident.

Visa interviews are offered only at U.S. Consulates (abroad). Once your mom receives her conditional permanent residency, you can file for adjustment/follow to join.

If your mother comes to the USA to activate her new green card, you can immediately file an I-485 application for permanent residence. It may take about 6-7 months to get work and travel permission, during which time you can''t leave the USA. Most get their green cards within a year or so.