The BEST thing you can do is to be there with them and make them feel every moment of being alive.
I was diagnosed with Stage IIA Hodgkins almost 2 years ago, a few weeks after my daughter's birth and the day before my son's second birthday.
I had a good prognosis and have luckily been cancer free for almost 18 months.
Regarding clinical trials and extending life as long as possible - please make sure that's what she wants. Chemo is very hard to go through. Sometimes, especially in terminal cancers, the wishes of the patient may not be to extend life. Regardless, I hope she makes the decision that is best for her based upon her wishes and her desire to fight.
One of my friends just learned her mother is terminal from stage IV, recurrent breast cancer after being clean for almost a decade. She has a 2 year old daughter who she desperately wants to know her grandmother.
Celebrate the life, be there, start helping her immediate family and remember the toll of cancer goes well beyond the time in treatment, the passing of the family member.
When I was in treatment, I was mostly worried about my husband and my children if I didn't complete treatment successfully. The people who are left behind after the patient passes are often as effected (if not more) by the cancer.
I received a second opinion from Northwestern as well - excellent facility. Seek 3rd and 4th opinions if needed. Not all Oncologists approach things the same way.
I'd also recommend getting involved with organizations such as Imerman Angels (imermanangels.org) based in Chicago who provides networks for not only patients but also for family members coping with cancer in their lives.
Best wishes!