It was an arranged marriage.
An arranged marriage Astrid couldn't bear. She was forced into marrying you for the sake of an important alliance with your tribe and hers, Berk. Astrid didn't want to get married to someone she didn't know.
Sure, she'd never really been much of a romantic, but she certainly still wanted at least some history with the person she was going to share her last name with, tied with forever till she reached the end of her life.
Her father, didn't seem to regard Astrid's concerns, as soon enough, Astrid was waiting on the shoreline, Stormfly by her side, her father on the other, as Berk's people awaited your arrival, ready to welcome you with open arms.
Though Astrid was still very much against the idea of marrying someone she never saw, she at least tried to get along with you.
It was not like she had any other choice.