My own rant is my friend's husband beat her last night .. she texted me a photograph this morning of her badly bruised abdomen. I don't know what to do.
Even if she won't call the cops herself (and that being the case, no, you shouldn't either, because jeez, what if her husband answered the door to them?), obviously she trusts you enough to tell you about the abuse, and that could be seen as a cry for help.
Sooo... does she want to get out of the house? If so, maybe you could offer her a safe place to sleep tonight? Not necessarily
your house (especially not if her abuser also knows where you live), but maybe you could offer to take her to a motel or something, and pay for her room, so he can't so easily find out where she's gone (e.g. by calling taxi-companies, or checking her credit-card transactions online).
Does she have any kids? Depending on age, that would make certainly things a little more complicated (if she took them with her without first reporting the abuse, I could well imagine an abusive husband calling the police himself, to report a 'kidnapping').
But at the end of the day, she is an adult. So, much as you might fear for her (and I do too, for whatever that's worth), you can't
force her to accept an offer of sanctuary -- but at least she'd know she has a way out if she needs it.