Sex trafficking is basically when you break immigration laws and/or forcibly transport people against their will, or in some kind of unescapable debt/slavery type of arrangement, where you yourself know that the people you are illegally moving are going to be forced into sex work, often for little to no pay, often with the sex trafficked people having no practical ability to leave due to withholding their passports or bank accounts from them.
EDIT: And also often getting the sex trafficking victims addicted to drugs.
Its human trafficking + facilitating or operating a business of prostitution or non consensual pornography production.
Unless you are going to be forcing your gf into prostitution as her pimp following your out of state dinner, then no, what you have described is not sex trafficking.
If she is unhappy with going to an out of state restaurant but ultimately consents to this, and then consents to sex afterward, this is just an awkward relationship with you being pretty weird and controlling, but its probably not a crime.
If, however you threaten her or force her or drug her to get to this out of state dinner, and the do the same to coercively have sex with her without her consent, then that's interstate kidnapping and rape... still not sex trafficking though.