You are assuming a lot from her silence no? Personally I think she finds him oblivious, snobbish, irritating, pushy and many other negative qualities besides which I agree he does not feel the need to hide.
The thing is although Jill may be comfortable with the MC she is in fact very introverted and has difficulty expressing her opinions, especially with people like Tybalt who is a born bully, since it is hinted that she herself had to deal with some kind of harrasment issue in the past.
Her inner strength shows only a few times when trying to protect the MC and yes she particularly abhors violence of the physical kind.
There is never a scene in which Jill openly criticises him, either directly (where we could say she does not do so out of politeness) or indirectly.
Even during the presentation, Jill is thinking about Bella who might be upset, not about the fact that Tybalt is talking nonsense.
a person who had framed a minimum Tybalt could never believe the tale of his heroic deeds that puts out the fire by sacrificing his tailor-made jacket, no one.
while there are numerous scenes in which Jill is openly sympathetic towards him, when he interrupts her yoga class, when he cheers her up after the theft at the preps... even when Bella proposes that Jill hook up with Mc, Jill is worried about how Tybalt might take the news...
Jill has two friends: Bella and Mc, both of whom hate Tybalt more or less openly, yet Jill never criticises him.
but it doesn't seem strange to me, the social distance with MC is huge, in reality it would be almost impractical, that Jill is comfortable with Tybalt is not strange.
