Merging two families into one can be extremely difficult.
Perhaps not in the day-to-day, but when traditions are called into question, anything could happen.
If a sister-in-law doesn’t like you, she can cause plenty of stress in a marriage.

Accepting this mutual silence only perpetuates bad feelings.
Start by trying to understand where she is coming from ,such as a place of jealousy.
Make your moves and talk to her while feeling empowered rather than feeling like you are being controlled.

This should be done with care and empathy, though.
She needs to do the same, but you might have to be the leader.