I have recently made contact with a putative (half)-first-cousin with whom I may share a grand-father. There is not a definitive documentary trail that confirms her grandfather and mine are the same, just some very suggestive evidence that our grandfather first married my grandmother and then married her grandmother (a marriage which has always been known to be bigamous in her family, which could explain the naming discrepancy that we're seeing).
I'm hoping she'll agree to DNA testing to resolve any lingering doubts, and want to understand how our relationship is likely to be predicted by a DNA testing company, so that if we find there is a match, we can assess how far back it goes. (It isn't, of course, impossible that we're related via a different route -- her grandfather could be related to mine rather than identical to him, for example).
Is there a reliable on-line reference for assessing the likely relationship between two individuals based on an autosomal DNA match?