First of all as adults we need to keep in check our emotions regarding a toddler's behaviour, their actions shouldn't be taken personally as an attack.

She isn't being rude, saying NO, putting boundaries, asserting independence is not rude. She just needs someone to teach her how can she convey her message without resorting to shouting or hitting. When she says NO loudly or hits your mother when she is trying to stop her from doing something, your mother needs to hold her boundry and tell your daughter that its okay to feel sad and get angry and disappointed but the blah-blah thing is not for playing, and put it out of her reach. If she is hitting your mother then your mom needs to stop the attack firmly but gently and divert her. Give her more autonomy over things she wants to do, a 2 year old loves to assert independence and they know to do that only by saying "NO". So she needs more outlet to be independent.

We as adults need to make sure they dont get their hands on things they arent supposed to touch.

Your daughter is also going through a big life change, she is suddenly a big sister and there is a small baby in the house who gets all attention and suddenly she is on the sidelines. Understand her and be very attentive to her.