As someone who's been on the receiving end of a cancer diagnosis, too, the only thing I wanted at the end of the day was to spend time with the people important in my life.
Yes, call. Don't script what you're going to say. Just talk to her. Ask her what she needs, how you can spend time with her, what you can do for her over the next few days, weeks, months.
As a cancer patient, you find yourself reassuring other people about your condition to a greater extent than you really receive it yourself. In my case, cancer taught me how much I wanted to live. I'd just had my second child and celebrated a birthday 2 days later. Everyone is different, but the desire and need to feel loved and alive is pretty consistent.
Ask her how she'd like to be remembered and how you can help her accomplish it - and most importantly, don't make it all about the cancer. I just wanted people to make me laugh. It made me feel very alive.
Good luck.