If you are 25 with a 17-year-old girlfriend you are in love with and her parents are truly against it could you leave together without being tried for kidnapping?

Not knowing the state of residency it is not possible to speculate on the legalitites of the situation except in a general sense. First of all kidnapping charges only apply when a person(s) are taken against their will, therefore that issue is not relevant. The safest option is to wait until the young lady reaches the age of majority for the state where she is presently living. It would most definitely be a mistake to take her (even though she is willing across state lines;that could result in federal as well as state charges. Assuming she is of the age of sexual consent there can still be applicable laws such as corruption of a minor, violation of state compulsory education codes, coercion and/or intimidation of an underaged person, etc. Before making such a serious decision it would be wise to seek legal counsel. At the very least research state statutes for all violations and penalties pertaining to the specific circumstances.