I'm with you Nellie, the late QEII's practice of loaning jewels was the best solution.
I agree with the YouTube presenter that it would be lovely if Countess Alexandra returned the Alexandrine Tiara back to the the Royal Family. If she's keeping for one or both of her sons to have a tiara for their future wives...I really don't see that happening. Nikolai or Felix don't carry out any Royal engagements nor have they been included in any Royal banquets/State visit etc. Both are leading lives as private citizens, more or less.
There's the animosity over the titles being changed, so I'm sure that's another reason for the distance between the grandsons and their grandmother and the now King and Queen. I just hope Alexandra doesn't hold on to the tiara out of spite. It was a mistake to give her the tiara, but at the time, I admit I thought it was a lovely gesture.