Nope, seems to be real albeit not Tweeted but a joking round with someone at PBS
Clinton’s recent reentry into the public sphere after months out of the limelight has led to speculation that she could be seriously considering a rematch with Trump. Those questions have been stoked by Clinton herself, who responded to a recent Trump tweet about her running again by simply saying, "Don’t tempt me," and joked with PBS’ Judy Woodruff about a possible round two with the President.
“Maybe there does need to be a rematch,” Clinton said jokingly. “Obviously, I can beat him again.” Clinton bested Trump in the popular vote, but fell short in the Electoral College.
TBH I would just read the ‘I can beat him again’ as pure Trump baiting, trying to get him to go into frothing justification of how he won despite losing the popular vote, even though he doesn’t have to.