Definitely. My fave inspired Beyonce to go solo, inspired Gaga to play the piano, inspired Rihanna to move to the United States and inspired Katy to go lesbian with I Kissed A Girl.
Yes. From Christina Aguilera to Rihanna to Selena Gomez to Lady Gaga to Miley Cyrus to Beyonce to Girls' Generation, etc. Most influential pop female of the last decade
She's been heavily influenced by Michael Jackson, Madonna, Mariah Carey, Whitney Houston, Shania Twain, Janet Jackson and so, so many more.
Kelly has influenced a good few but mainly Demi Lovato. Gaga has influenced a good bit of her contemporaries as well to be bolder with their performances/costumes/etc.