The video deposition is not simply a continuation of the previous deposition, is it? Not all depositions are completed in a single meeting.
For information purposes only, here is a link to Missouri Rule 57, Interrogatories and Depositions (see 57.03):
https://www.courts.mo.gov/page.jsp?id=881
Your mom can object to sitting foTr a second deposition, by the way. The other party would have to justify their need for one. Your mom's attorney can discuss with your mom the other party's reasons for scheduling a second deposition.