It depends on how she will use it. I have used Google Chrome on a Windows computer and quickly found that I picked up a lot of malware that was not able to load from using Firefox or Internet Explorer. I spent a week and nearly $100 to get the malware completely removed from the computer and now avoid using Chrome completely.
I would not use the Chromebook for any transactions that I wanted to be 100% secure. I would trust an iPad.
The majority of companies IT people are buying iPads for their tablet users and not the much cheaper Android tablets and the reason is the much better security provided by the more modern Apple operating systems.