some background on Nikita's and Elena's partnership and relationship, and a partial link to Morozov.
Nikita, from the very start and to the last day, made Elena to some degree quite insecure, as a skating partner and as boyfriend.
when they were pre-teens they skated at the same rink, lots of girls, just few boys. Nikita was a crush for practically every girl younger than him, including Elena. At one point, Elena was asked if she wants to be his skating partner and she eagrly agreed, it was also "on words" agreed by Nikita, and by coaches and by their parents. Yet Nikita, to keep up his value and importance as "a rooster in a chicken yard", made an official announcement that he wants official try outs with other eligible girls, including Elena (whom he already agreed to pair with). That made Elena feel very rotten and she openly wrote about it in her memoires few years back (before their break up).
When they skated and had the relationship together, he gave Elena an impression that "he is one of a kind and there are many girls out there". Even in their body language it could be seen, like on photos where (often but not always) he is standing tall and proud with this arms crossed, while she was bending over him or clinging/hugging him and looking like an "attachment to an independant selfsufficient entity".
The more obvious photos are from the time they visited New York, but i can't find them quickly, yet i made a comment about it, back then here on FSU, expressing concern.
The team/couple had occasionally very hard times, and Elena often felt those "old waves of insecurity" as a skater, and sometimes as a female, since Nikita held an image of "just walk around me, and you will see no strings attached"..
Like some females who feel insecure with their men and seek approval from others, Elena started flirting with Morozov, and he did not object or missed this opportunity...... It did piss off Nikita, and the relationship started to detiriorate.. His solution however was not to change himself, but to chage his partner.. and the rest is history...
I don't know if Nikita slapped Elena like he did Vika, but the situation in Canton already showed that he was capable.