YA book about a girl who lives with her family on a fleet of ships, but gets stranded on land

[Shade]

I remember reading this book around 2013, probably. I rememeber the girl had another sibling, possibly a sister. The fleet of ships stopped at either a port or an island to restock on supplies and she was left behind. They wouldn't return for another year, so they all thought she was dead. She finds a group of people either living in a cave or underground and she survives with them and finds love among them. She returns to the trading port where she lost her parents, sees them ln the ship and they're reunited but she chooses to stay on land.

[Rainbowheart]

How old was the girl, teenager or younger child?

Was it historical fiction or set in modern times?

What part of the world were they in? Was it a tropical island or cold weather island?

[Shade]

Teenager, I believe, but I'm not sure.

Set in modern times/the future. I can't remember if it was an apocalyptic type event which caused the fleet of boats to be a way of survival or if it was an alternate Earth.

They sailed around the world, hence why it took a year for them to get back to her. I think she was stuck on an island with variable weather, though they did have to close the gates/cave or whatever they used for the winter months due to it being practically uninhabitable and due to the threat of wolves or some other predator.

That's about as much as I remember.