No. Her poll numbers were falling before that, and at the absolute most Wisconsin and Michigan might've stayed D. The overwhelming majority of voters had already made up their minds before the Comey letter and probably anyone who used that as an excuse not to vote for her wasn't planning on doing so anyway and would've cited something else instead.
PA was about as close as WI was, though. If WI flips, doesn't PA also have a decent chance of flipping?
BTW, the race might have gone into the House of Representatives had Trump held PA but lost MI and WI. It all depends on those two Trump electors that went rogue in real life.
The margin in WI was half of PA. MI and WI also had huge reductions in vote totals for both parties compared to 2012 so it's at least plausable that enough people changed their minds and skipped the Pres vote afterwards to make enough difference to flip the state. Pennsylvania by contrast had Hillary down about 65k votes from Obama in 2012, but Trump was up almost 300,000 votes compared to Romney, so given the massive change in the R vote, and that I doubt people switched from Hillary to Trump over the Comey letter, and that Hillary was likely to be down from Obama regardless, is largely why I don't think PA would've flipped.
But in the end, one's view of how Hillary would've done without the Comey letter depends entirely on how they feel she would've done without it.