She was stunned when she found Carl had sent her his suicide note along with an encrypted drive. What did he want from her? Obviously whatever was on there was extremely important, but she couldn't find anyone who could remove the encryption.
She realized she had met a dead end, and she decided that she would ask Nico for help. In their dealings with the Hawks, he had shown himself to be a man of his word, and if she asked for his discretion about Carl and the drive, she thought she could trust him. This made her sad, because a year ago, she wouldn't have thought, she would have known what to expect from him.
Sure enough, he agreed to help her. His first request was to take the drive from her, but she just couldn't. She needed to hang on to it. Nico's feelings seemed hurt, which surprised her on some level - did he really think she would unquestioningly hand it over considering how secretive he had been, and how completely he had jettisoned their friendship before?
Later she reconsidered and asked Nico to hold on to the drive when she found it after it had briefly gone missing from her purse. He asked then if she trusted him, and she said no, but softened it by saying she didn't really trust herself right then.
When he came over with the encryption software to find out what was on the drive, she felt glad she had him on her side. He hadn't let her down about this, and he would be a big help in understanding what Carl wanted her to do with the information.