Ghost story, meets love story, meets superhero story.
A hundred years ago, 17 year old Lizzie died. Since then, she has been invisible to the world and unable to interact with anything. A mere observer, Lizzie wandered the world looking for some meaning to her existence. Then she met Jeremy, a shy 18 year old boy who inexplicably has both the ability to see her, and the power to make Lizzie solid with a simple touch. Together, they find that Lizzie’s ghost powers are able to work on Jeremy, and through him, on others as well. The two of them are suddenly able to help where no one else can. And this power attracts attention, some good and some definitely unwanted.
My Ghostly Girlfriend by Michael Slentz
https://www.amazon.com/My-Ghostly-Girlfriend-Michael-Slentz-ebook/dp/B0F8Q6DKW6