Evidently since I’m still not seeing it.
No, she didn’t. She wrote:
First she noted that she’s not arguing the point, so she can’t be using the Bible to back up her claim since she’s not making a claim.
Second, she noted that she didn’t know the expression of the other person’s faith which leaves open the possibility that other people have different belief systems and don’t necessarily believe as she does.
Third, (I’m leaving this point blank in defiance.) 
Fourth, she said it’s just a point to ponder. She didn’t say that everyone should believe it as well.
From my own perspective, since I don’t know hers, I think you misunderstood her point. I personally believe that everyone loves themselves is true because at the very base level, they have a preservation instinct. And while people might not like themselves much and try to hurt themselves, this primal instinct can be deemed a type of love as mentioned in the Bible.
Do I like people spitting out Bible verses in posts? Not so much.
But I also think there are ways to combat the lack of logic that are better than just making blanket statements.
A better response to her “why d’you suppose” question might be to note that the Bible might say that because it may be written by people who felt that way at one time. . or whatever it is you suppose.
Again, I disagree with your characterization of her reply. Her post is here:
Soul Brother Number Two accused her of witnessing. She disagreed saying that she was just giving her opinion based on her worldview. She was just noting that her view was not less valid than his and noted that others believed as she did, although perhaps not a lot of people here at the SDMB believe as she does.
Soul Brother Number Two went on to agree with her later, evidencing that she did have a point.
She didn’t use the power of the numbers to prove her point, and she didn’t walk away in a huff as you suggest.