Good for her for being able to articulate this to you at her age. Can you tell what might be spurring her interest? If it's a friend or older mentor, could she explore attending the same church as that person and you could see if it's a good place for her to be baptized? Overall, I think with any religious community, it's the community that is important, so finding her a friendly place to plug in where there's a good youth group program and solid teaching/mentoring from adults you feel you can trust is critical. Among various Protestant denominations, there are lots of warm, accepting churches in this area. We are Episcopalian and have a great youth program (All Saints), but there are lots of churches that fit the bill including local Methodist and Presbyterian churches. If you feel comfortable saying the general area where you live, perhaps others can recommend specific churches to explore.
In terms of other resources, here is a high-level guide to some key denominational differences that might be more helpful for you. A lot of these distinctions will be lost on a 9yo (which is probably as it should be!)
https://www.learnreligions.com/comparing-christian-denominations-beliefs-part-1-700537
But for kids, here is some age-appropriate reading that focuses more on fundamentals shared across Christian denominations:
https://www.amazon.com/gp/product/1400316022/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/What-Bible-About-Handbook-Kids/dp/1496416112