Obviously, I don't know the inside of the relationship any more than you do -- but no less either. IMO it may not speak against his "credibility" so much as for his Christian charity. IIRC, C.S. Lewis gave money to many people (and many of them women) over the course of his life as acts of charity; when he died, it was discovered that he had been giving away 2/3s of his income this way. Many times, the gifts were repeated and spoke of an on-going relationship. He exchanged correspondence with quite a few for years (he died before cell phones!). Does this mean he was having or wanted a sexual affair with all of them?
Also, in modern American usage, "friend" is kind of a catch-all term in most cases for someone we know and don't have an actively hostile relationship with; probably well under 1% of people referred to as "friends" describe the sort of relationship Cicero writes of in the De Amicitia!
As to the people who think it's significant that she had his cell phone number, don't most people in business nowadays have their cell phone number printed on their business cards, along with their office phone, fax, etc.? And most seem to pass out their cards to anyone who will take one!
I gather this woman too had an NRA connection, though I don't recall seeing exactly what it was. And I do wonder how that reporter heard of her in the first place. Did she call him out of the blue? What does he mean that he was "working on" the story for a week? Couldn't she predict that she too might be "reviled" or whatever like the other accusers in that her background is just as full of red flags? Is someone paying her?
My personal "sense" - and this is perhaps intuition along with life experience - is that of troubling inappropriate behavior.
I can readily accept that the accusations are trumped up, false, perhaps even a conspiracy. But what concerns me are attempts to excuse or make light of what is clearly unacceptable behavior (again, IF the accusations are valid). For example, I believe a married man has no business "going out for drinks" with another woman while on a business trip, singling a woman from the audience out and trying to arrange dinner alone with her, inviting her to his room, or for that matter calling another woman in the middle of the night.
I recall how Billy Graham would not travel with a woman or even be seen with a woman privately without someone else around. Someone said today that he would have someone check out his hotel rooms to ensure no one was lurking there to possibly cause him scandal. IMHO that's the gold standard.