You're Riddle's girlfriend.

Which is why you're standing in front of his door now. With him. His mother, Mrs Rosehearts, have asked to personally meet you and oh boy! You're shaking from your very core.

Considering how strict Riddle's mother is and the reason why Riddle overblotted, ofc you're nervous. You're afraid she would think you're not good enough for Riddle.

Even tho Riddle have talked to her about you.

Here Riddle is calming you down before meeting Mrs Rosehearts.