One of the biggest problems a guy's response to a LJBF rejection (and that's what it is, a rejection) is in determining whether or not she was 'really' interested (i.e. a sh!t test) or she meant it as an exit strategy. It's this AFC, hopeful doubt that throws guys off, but In either case the default response should be a takeaway.
Women have used the LJBF rejection for hundreds of years because it serves an ego preservation function for them. To a greater or lesser degree, women require attention and the more they have of it the more affirmation they experience, both personally and socially. The LJBF rejection has classically ensured that a woman can reject a man yet still maintain his previous attention. It also puts the responsibility for the rejection back on his shoulders since, should he decline the 'offer of friendship', he is then responsible for entertaining this friendship. This of course has the potential to backfire on women these days since the standard AFC will accept an LJBF rejection in the mistaken hopes of 'proving' himself worthy of her intimacy by being the perfect 'surrogate boyfriend' - fulfilling all her attention and loyalty prerequisites with no expectation of reciprocating her own intimacy. The LJBF rejection also serves as an ego preservation for her in that having offered the false olive branch of 'friendship' to him in her rejection she also can sleep that night knowing that she (and any of her peers) wont think any less of herself. After all, she offered to be friends, right? She is excused from any feelings of personal guilt or any responsibilities for his feelings if she still wants to remain amiable with him.
The difficulty I have in questioning the veracity of an LJBF, wondering if she was 'for real' or not, is it still keeps her in a position of control. I think the default response should be to assume she is serious and take it as a rejection (and her loss) ergo, you remove the reinforcer - attention. Up until the point you make an approach for her intimacy she was enjoys the benefit of your attentions. After an LJBF response her latent intent is to keep that reinforcer of attention. Do not reward her for this disingenuous response, she will only use it on you again or with another guy in a similar situation since it was reinforced the last time this circumstance was experienced. And should the next fellow reinforce it further she will internalize this as her standard response.
A man's default response should always be to excuse him from the situation. The reason for this is because it serves his best interest whether she is testing him or is rejecting him. If he is confident enough in himself to walk away from the sexually tense environment, she helped create, he proves himself as decisive enough to put himself above being 'played' like this. He leaves her with the impression that he is the PRIZE, has options with better prospective women than disingenuous girls such as her and is confident enough to take away his attentions and thus passes her sh!t test while placing the responsibility of a re-connection on her (where it should be anyway). If she has in fact had a change of heart (her prerogative) and is using the LJBF as a means to reject him, he still benefits from all of the above and plants the 'seed of doubt' in her about her initial estimation of his acceptability for her intimacy. Let a woman's imaginations work FOR you. And even if she is truly not interested in the guy, he walks away on his feet and not his knees, playing friend with her and wasting still more time that could be far better spent with more productive prospects.
This is really one of the few win-win situations for a guy to make a wholesale withdrawal of his attentions when he is confronted with an LJBF. Women know all too well how an LJBF places social pressure on a guy to accept what basically amounts to an ultimatum of negative social proof and that's a hell of a sh!t test no matter what her real intent is. If the guy turns down her offer of friendship, he's the d!ickhed, not her. But the guy that can do what common sense and gut instinct points out to him will be the one to succeed, with her and himself.