She doesn’t hate you. If she did she’d not let you pet her. The biting your ankles when you go into her pen sounds like “cage aggression”. You’re in her territory. This is not uncommon in female rabbits. It is an instinct. You and she don’t know each other very well yet, so this could get better with time. For now aid try to stay out of her pen until she feels safer in her new environment.
If she bites your arms and thighs when she’s in your lap it could mean she wants to be put down on the floor. If it’s not that, it could be some form of grooming that she isn’t very good at. You will need to communicate to her that the behavior is not acceptable. If she wants to sit in your lap but bites you, I’d put her back on the floor. Maybe with a firm “no”. If she bites you because she wants to be let down on the floor, try to not hold her at all, but let her come and go just as she pleases. If she gets what she wants by biting, she will keep biting. That’s how animals and humans learn things: by trial and success.
She’s all new in your home and getting a new home causes stress -even if she now is in a very much better home. I’d not switch her from one pellet brand to a new one straight up, you should do a gradual switch. She’s used to yummy but not so healthy food, she might refuse the healthier food and the new food can cause tummy upsetness. Different gut bacteria are needed for different types of food. Her tummy needs time to get used to the healthier food.
If she’s used to carrots she could get pieces of carrot as treats. With rabbits you never want to do radical dietary changes. If her droppings look good you don’t want to disturb her gut. Go really slow. Does she eat hay?