EVERY Straw Hat could react to Big Mom's speed before she got super thin, so there's no question if Kuma or Barto can catch Big Mom; It's a question of how their fruits react with her own and herself. Kuma can maybe, just maybe, push the souls out of her major homies and send her flying. I'm assuming Big Mom could probably resist it though since that ability seems to operate by physical force. But even if she stays, she's no monster with her physical strength countered and homies gone.
Doflamingo's the real problem here. Both Kuma and Barto are limited in how much area they can block while against a guy that can turn their entire surrounding into hostiles. Team 2 wins. Fending off Big Mom requires at least one of them to actively watch and counter her attacks, leaving the defender vulnerable, and the other person up for a 1v1 that they're bound to lose.