She took her down twice. Once in the first, once in the second. Ribas took Dern down both times to show her she was not scared to go to the ground with her. Which is why 90% of the fight took place on the feet.
They aren't at the same level in terms of 'grappling', Dern is a former world champion. Ribas though is better at using her grappling offensively because she is much smoother at getting her opponents to the ground than Dern; because of the judo.
Dern was in shape enough to make 115, calling her 'lazy and out of shape' or saying 'she was not training' are just excuses used to discount Ribas' domination of her. And if you watched that fight, which it sounds like you did, I am sure you would agree it was pure domination and Dern looked like a minor league fighter out there.