Ahh, that is what you meant by her logging on, OK. I do some financial stuff online, but it is limited to checking account balances, that is it. Well outside of buying stuff off the Internet but I only do so at trusted well known sites no matter how good the deal. If it is phishing and they drain your account, it wasn't such a good deal after all!
Always close your browser out after logging off. Even if you want to keep surfing, close the browser and clear the cookies and cache and then open again to do the rest of your surfing. The most common way they get you is by viewing what you are viewing and if you don't log off but instead just close the browser well now they are in your account!
They will also raid your cookies and cache for saved passwords. But, like I said, when it comes to my bank accounts or any account that would let you transfer money online, I disable that feature so the only thing you can do is look at transactions and balances.
As you said, can't be too careful!