The drama with her is 100% real - she was a major part of the Vinesauce fanbase at the time, and did a lot of fanart for the streams/had a personal relationship of some kind with Vinny. If you google that handle, you can find her old formspring account where she answered some questions about the situation with Vinny (pretty vaguely, but it does confirm that it happened). To what extent she was connected to him is where the confusion comes in.
The chat log I linked was from /v/, and as you pointed out, it was supposedly debunked because of some inconsistencies with the timeline. Regardless, I definitely believe that Vinny and SgtFgt were doing the ol slip n' slide, and the fact that the logs were allegedly posted on /v/ by her makes me feel like, even if they are fake, there is truth to them. Plus, as I said sometime earlier in the thread, there's a recurring theme of Vinny being a boob guy, since in the logs he refers to himself as a "tithound" and other weird shit, while in an official Vinesauce video (the drunken CSGO one), he tells a story about a friend who nicknamed him "The Tit Doctor." Not hard proof, but definitely something to consider.
I'd be pretty interested in having someone who was more cognizant of the SgtFgt drama talk about it. I was a fan at the time so I knew that some behind the scenes shit was going down, but I was pretty young, so I didn't know where it was happening/how to find out about it. The real gag will be if SgtFgt herself rises from the murky depths and drops a bomb on everyone that it was all true and she has evidence to prove it.
As for Vinny being a lonely fuck, you're right, but at this point it seems pretty self-inflicted. He's clearly charismatic and charming, and he had a great few years looks-wise where he definitely could've gotten any nice, nerdy chick that he wanted. (He's still attractive now, but that hair... ugh.) If you saw it before, we talked for a bit about some very old forum posts Vinny made (around age 19) where he talks about sleeping with his best friend's girlfriend, and the heartbreak from that relationship is implied to be the reason why he hasn't pursued anything serious for such a long time. That's all conjecture, of course, but it's something to note.