Let the skating begin
We won't know for a while. One thing about having the ***** is the variability of exposure. A mild case may differ from a more severe case. I'd get the vaccine if I were her. Then she can come visit her Mama this summer.Vaccines are freely available in shopping centres in Moscow.
Given Tiff has no antibodies 7 months later, it would need to be a bi-annual vaccination unless the vaccine antibodies last longer.