Her father

Under cover

"No, dad please you can't!" Bella cried, panic in her voice.  Her father's face remained stern and certain.  He didn't want to break his daughter's heart like this, but he had no choice.
"My word is final, Bella.  You are not to see Ellie again.  She is a terrible influence and you haven't been the same since.  You haven't even let me meet the girl!"  He explained.  Bella knew that once her father made up his mind he wasn't going to change it.

Bella would have to get a bit creative.  She took a deep breath, dried her eyes, and laughed.  This completely threw her father off guard.  He looked at her desperately trying to understand.  Still with a giggle in her throat, she got out her phone.
"What are you-" her father started but was cut off by Bella holding up a hand, indicating for him to wait.  Once she had found what she was looking for, Arrabella turned her phone to her father, revealing a picture of the girl she had been dating.  Moriarty recognised her instantly as Ellie Holmes, daughter of Sherlock.  Anger bubbles up inside of him and he turned to ask Bella but she answered before he could.

"I'm under cover!" She explained, "I don't love her, I don't even care about her, I'm using her for information.  I didn't tell you because I didn't want you dictating my mission." She took a deep breath and lowered her voice to say the last part of her speech, "I just wanted to prove that I could help you."

James Moriarty was in shock.  He wanted to be proud of the girl but he couldn't.  He hated how his line of work endangered the only person he was capable of caring about and now she had undertaken a mission alone that could endanger her further. Especially as he wasn't there to help her through it.  He was ripped from his thoughts when he felt arms around his side.  He looked down to see that Bella had moved round to hug him. 
"I'm sorry I didn't tell you, dad, but please, let me try again.  I'll update you regularly and make sure I stay safe." Bella said to him reassuringly.  Her father stood so that the two faced each other.  He now had to choose if he could risk Bella's safety to be able to take down Sherlock.  He knew how precious Ellie was to her father and now he had a direct link to her.  Hesitantly, he nodded.  Bella smiled brightly and hugged her father tight.  Before he had time to change his mind, Bella skipped off to her room.  Once safely inside she sent a text to Ellie that read,

Dad knows, plan UC underway, sort it out your end.