....Ps Has Vishneva not been introduced to the First Lady before at gala events?
Not Mrs. Obama, who has not attended a Kennedy Center performance yet (ballet or otherwise), other than the Inauguration & the Kennedy Center Honors. Mrs. Clinton used to attend ballets, although it helped that daughter Chelsea was/is passionate about the art.
Of course, Vishneva has met the Russian First Lady.
Michelle Obama gave a speech at ABT's Met season opening night gala last year. I'd be surprised if MO hasn't been introduced to the principal dancers backstage, or at least to the dancers who performed that night which included DV. So there's a very good chance that DV has been introduced to MO. If MO endorses an organization by giving it a speech, she should be familiar with that organization.