So T'Pring didn't want Spock anymore as she'd grown attached to another guy, she was taking a big risk that the victor of Spock's battle didn't decide to drag her along and make her live on the Enterprise anyway.
As Spock said, T'Pring's logic was flawless.
This thing that happens every 7 years to every member of their species that is so embarrassingly super-secret they never talk about it to non-Vulcans ever, yet they have this grand and pompous ritual ceremony where they invite their nearest and dearest to attend?
Vulcans' "nearest and dearest" are not Vulcans. T'Pau made mention of this, specifically questioning Spock's choice of "friends". Later, she praised Spock for those same choices.
Many human groups on Earth today are also very private. Try crashing a KKK meeting, Shriner's ritual or Amish ceremony if you are not already an indoctrinated member. The outcome could be more unpleasant than a dressing down by T'Pau!
“When all Americans are treated as equal, no matter who they are or whom they love, we are all more free.” -Pres. Obama
"A great democracy does not make it harder to vote than to buy an assault weapon." -Pres. Clinton