Can H4 VISA holder with new H1B 797 get H1B VISA stamped in Mexico?

Hi, My Spouse(Indian Citizen) in the U.S had got her H4 VISA stamped on her Passport but recently she has got her H1B I797 with a firm. We want to get her new VISA stamped as H1B for India travel but no appointments.

Wondering if she can go to Mexico or Canada for the H1B VISA interview and stamping. Please let me know.