Mysidia is an adoptable script.
It's a bit of an advance script in my opinion.
I'm not sure it suits what you might want or need.
I thought instead this would be better for you:
http://www.myvirtualpetsite.com/
It allows you to create a virtual pet site like neopets, without having to need to know how to code, or have to pay for hosting. My younger sister also wants to run a Virtual Pet site, and I plan to get her to use this site.