It's also the reason why Diana got so much denial on her heart because she always thought it too deep and didn't know the essence of their relationship. The core and lesson that Mia should give because it's crucial for her and also for her future.
"Because you should trust him, Diana!!!"
Mia couldn't help herself to scream because Diana was so hard to tell. She's a smart person but in this subject, Diana couldn't understand more than she did at the office. It's just a matter of feeling and Diana wasn't sensitive enough to understand other people's feelings even her own boyfriend.
It's like slapped at her face when Mia said it. She thought that shouldn't be that rude but Mia didn't care about it. That's probably the last thing that she could do to make Diana understand how important to trust someone.
