Jessie is an important character in Toy Story. She's a toy with a lot of energy and enthusiasm. She has a backstory about being abandoned and then finding a new family with the other toys.
Yes, there are likely many out there. You can start by looking on popular fanfiction websites like Archive of Our Own. Just search for 'Jessie Luke and Jessie kiss' in the search bar, and you should be able to find relevant stories. However, the quality can vary greatly, so you might have to read through a few to find one that really suits your taste.
For Jessie, you can develop her by showing her growth in terms of her relationships. If she's shy at first, show how she becomes more confident around Tony and the other Jessie. Tony can be developed by giving him a backstory. Maybe he has a troubled past that makes him more empathetic towards the Jessies. The other Jessie can be developed by highlighting her differences from the first Jessie. For example, if one Jessie is more artistic, the other could be more scientific, and show how they learn from each other.
One possible plot could be that Jessie and Luke are friends who gradually develop deeper feelings for each other. They might go through some adventures together, face some challenges that bring them closer, and finally share a kiss in a moment of realization of their love. For example, they could be working on a project and start to notice little things about each other that they find endearing.
Jessie Keane is likely an author in the realm of Fantastic Fiction. However, without more context, it's hard to be very specific. Maybe she is known for a particular genre within it, like mystery or adventure novels.