Fencing, then jousting-on-horses.
(befitting their royal stature)
If they're 1-1, and uninjured, after the 2 royal events, then a women's Mixed Martial Arts bout, 5 rounds, to break the tie.
<All 3 of the above are more dignified than the omni-channel multi-media catfight they've engaged in since the Oprah interview.>