Ignore Marina's advances in the first 20 days. When the trial period is over, you give her the option to wait.
When she offers herself to you after a certain event that night, you still reject her. That will make her "hate" you, but that's when you have to talk to her the most. Be careful, just talk or play games with her. At some point, she'll open up to you. I think it's on the night of lightning. From there, all you have to do is increase love to 1k and lust to 250, which is what she asks for to get everything.
edit:
In the first few days, I recommend only saying good bye to her when she goes to the school in the morning to raise love as quickly as possible. From there, during the rest of the day, work on clothing to farm money and level up your level as a tailor.