My colleague is correct. You are messing with fire in this situation. Under the right circumstances you may face up to 99 years or life in prison.
A person may not have ANY sexual contact (penetration, rubbing, touching genitals, etc.) with a person under the age of 17 years UNLESS you are no older than 36 months from the person under the age of 17 who would be the "victim" in the situation.
For example: an 18-year-old may have consensual sex with a 16-year-old.
There are also other requirements for the 3 year exception such as not being a registered sex offender and not being presently married to someone else.
Bottom line: it is a HUGE risk, just don't risk it.
You should consult with an attorney for a more in-depth analysis of your situation.
Finally, even if the 3-year exception applies, you may not take sexual photos or video of a person under 18-years-old (no exceptions). Sexual photos could include clothed photos of the person under 18 in a provocative pose.
If by dating you mean going out, talking and being friends, you can do that. However, dating tends to lead to sexual actions, and this girl is too young for that. I strongly recommend that you find someone 18 or older to date, and tell this girl you like her, but not enough to risk arrest.