Spoiler: NERRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRD (click to see content)
There's a bit to unpack here. The other girl is Rin Tohsaka from Fate/Stay Night. She's a sixth- or seventh-generation mage who fights in a series of battles to win the Holy Grail, fighting alongside and against summoned embodiments of mankind's greatest heroes.
The mage crests (green glowing lines in the arms/legs) should've been more than enough for Rin to keep up. Essentially they're doing the same thing, loading chakra/prana into their limbs to increase their workrate, resulting in super strength/speed. But while in Naruto it's a special thing that's easy to screw up and only really available to fine chakra controllers like ninja medics (Sakura, Tsunade), it's a regular expected thing for mages like Rin to learn.
The explosions are her second-weakest attacks, where she lobs prana-loaded gemstomes at you. It's the beefiest thing Rin does in the first third of Fate/Stay Night, and the fistful of them she used to propel her would've been enough to kill Hercules five times. Literally, she fights Hercules, takes five of his twelve lives, and is still considered the more useless character in her team. Detonating them that close to her should've obliterated her.
By the time the story's properly ending her big drawcard is a jeweled sword that channels prana from the thousands of alternate realities' versions of her and uses it to cut demons in half with hyper-intensity rainbows.
Basically this fight was end-game Sakura put up against the equivalent of Chuunin Arc Sakura. End-game Rin is more equivalent to someone like Kakashi or Sasuke.