The Secrets of Heart Hall

Olivia Pamela Moore's mother died when she was 5 years old after she caught a deathly illness from her. Ever since then, Olivias father has ignored her and her younger brother has avoided talking because he was scared of her.
Olivia has to take care of her brother without him knowing, because her father is hopeless, so Olivia has to buy gifts and sign them as her father, she has to buy the food and pay the flat-owner while her father gets drunk.
Olivia acts out to try and be noticed, and to hide how guilty she feels about her mother dying and not her. She also gets stressed out to the point of yelling and fighting. When she acts out, she gets really angry and hurts people or breaks things.
After an accident, Olivia is sent away to live with her rich, kind Aunt Melissa and her cousin James. She is more lonely than ever, until she finds a secret door in the gardens, and goes through it to find a secret garden. While in there, she finds another secret door, which leads to another world, a world connected to the Moore family in ways she doesn't understand.
Olivia goes there every day, but still makes no friends. But then she meets her grandfather on her mums side, and he gives her some helpful advice.
Thinking of her Grandfathers words, Olivia starts being nice, and ends up making the following friends; Sophie Brown, her maid, James Moore, her cousin, and Isabella Smyth, the cooks daughter.
After a few amazing weeks, Olivia decides to show them the other world.
But when they get there, they aren't able to get back. And the world is cold, dark, and destroyed.
They need to figure out how to leave, but the citizens believe that girls should do housework and be controlled, so they're desperate to stop them.
Plus there's an evil sorceress destroying and enslaving the realm, one who's connected to Olivia in ways she couldn't even imagine...
So they must also save the realm, all while trying not to be killed.