Both women seem to be energetic and strong. However growth and agel will be size meaning. If Amber and Nina are similar growth, then Amber will win. If Nina is taller then she will beat Amber. The aside from of score the fight will be long and obstinate. Amber at the beginning will attack with fists. Nina will defend, but in knocks and slaps Amber will be better. Why? - She is younger and quicker .
If Nina will pretend to seize Amber's hair then Niny's chances will grow up. The women will pull at hair of every then. Time they will punch rival. Amber or Nina ( I would to the will she was Nina ) will overturn the rival. They will roll after the ground. They will pulls hair and to hit in face rival. Amber will be Nina in headlock. They will scrape rival. Nina first will begin pinching breasts and nipples Amber. I would to Nina will won. However I think objectively, that Amber will win.
Nina can beat many women in her age. Even a bit larger from her. Thin, average, fat... Nina will mount rival and to beat her. Rival will buck and to groan, wanting to free oneself. Nina however will force her to obedience and resignation the beating, pulling of hair and pinching the breasts. She will bully over helpless victim.
However if they are young athletic girls then they must be smaller from Nina.