We are currently in a long distance relationship that is going well.  The thing is, about a month ago her mother was found to have HPV.  They had determined at the time that it wasn't cancerous.

Last night she started crying on the phone and told me the news, her mother had cancer.  They still are waiting to find out what stage it is in exactly.

I honestly don't what I can do to help her.  All I can think of is saying "I'm sorry" and "It's gonna be okay."  I'm lost here, I want to make her feel better, but I don't know how.  

Any advice would be great, I just want to help.

If you want to help more, research the cancer her mother has.  That way, you can use the knowledge you find to be a comfort by mentioning treatment possibilities, or giving survival rates and recovery rates and such.  Also, sometimes you just knowing what your girlfriend is talking about helps her, because it shows a level of care and interest in her and her family.

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"Energizer Bunny arrested, charged with battery."