The girl called Cindy in Spider-Man: Homecoming is actually no other than Cindy Moon a.k.a Silk.
If you noticed a girl named Cindy in Spider-Man: Homecoming, you may or may not have realized that the film has introduced to you another super-hero. Marvel Comic Book fans now recognize Cindy in the movie as Cindy Moon, a.k.a Silk: the female counterpart to Spider-Man. And IMDB has revealed that the character will be featured in Avengers: Infinity Wars.
— IMDb (@IMDb) October 3, 2017
In the comics, Cindy got bitten by the same spider that gave Peter Parker his superpowers. She gets the same powers as him with the addition of organic webbings and photographic memory. She made her first full appearance in issue #4 of The Amazing Spider-Man back in July 2014. The actress playing Cindy is Tiffany Espensen, who is known for projects such as the TV series Kirby Buckets and the Easter Bunny movie Hop.
The size of her role is unknown in Avengers: Infinity War. With the film already packed with 37 main characters, it is likely small. But her introduction will surely garner her a much huge one in the future Spider-Man solo films.
Four years after the events of Guardians of the Galaxy Vol. 2, the Avengers, torn apart after the events of Captain America: Civil War, join forces with the Guardians of the Galaxy to battle Thanos, who is trying to amass the Infinity Stones for a gauntlet that will allow him to inflict his will on all reality.
Image Source: Wikia