How long have they been living together? Most rabbits do not appreciate having another rabbit come into their home. It would be like someone you have never met moving into your room with your knowledge or permission. If you do want them to be able to live together without issues, you need to take the time to introduce them before you put them in the same cage.
The smaller one is dominant over the larger one. She is claiming the food as hers and not letting the other one eat. Having 2 bowls in separate areas of the cage can help. Feeding them at the same time in separate areas allows for both of them to eat in peace.
Both of them should be spayed. Females can be very territorial. Getting both spayed can help with aggression. If can take a few weeks for the hormones to leave the body for you to notice a difference.
You might need to get a larger hutch. The vast majority of cages and hutches on the market are too small for a single small rabbit, let along a larger one or a pair. Building a larger one or adding a secure run can help.