what is a reason that someone would not like to meet Emily?
A reason, any reason? I guess that would depend on who you are asking to meet Emily. My brother, for example, would not like to meet Emily simply because she is a ten year old. He's not good with kids. No patience with them and openly admits it.
Personally though, I would keep my distance from Emily because she doesn't seem to have any qualms about hurting other people. She's upset when the cat goes missing after the hurricane, but personally killing someone or watching them sentenced to be hanged has little to no effect on her. She's cold.
After the kids are taken aboard the pirate ship, they are well cared for by the captain and crew. They are not treated as prisoners. While recovering from a wound, Emily feels threatened by a pirate prisoner. She kills the man, and is perfectly willing to let her sister take the blame for it. Later, the pirate captain is in the process of peacefully handing over Emily and her siblings to another boat for their own protection. His pirate ship is posing as a merchant vessel in order to not alert authorities to his presence. The children are being let go, free of harm. There is no reason to cause trouble for the pirates and captain Jonsen. However, Emily doesn't hesitate to alert people to the pirates' charade. The pirates are all captured, put in prison, and await trial. Emily is the star witness and lets everyone believe that Captain Jonsen is the man who killed the Dutch captain. Emily did the murder, but is perfectly happy to let a man that protected her and cared for her take the death penalty for her.
That's why I wouldn't want to meet Emily. She flat out doesn't have any empathy for anybody. If she's that cold at age 10, I can't imagine what she'll be like later.