what is a class d felony sexual abuse?

This is how the statute reads:
S 130.65 Sexual abuse in the first degree.
A person is guilty of sexual abuse in the first degree when he or she
subjects another person to sexual contact:
1. By forcible compulsion; or
2. When the other person is incapable of consent by reason of being
physically helpless; or
3. When the other person is less than eleven years old.
Sexual abuse in the first degree is a class D felony.

So it is anyone of those three things, but based on what you said it sounds like subdivision (1).

It is a classified as a Violent Felony, the maximum is 7 years in prison. If it is just one incident, not very severe, probation may be possible.

Also, Megan's law applies, so your friend may have to register as a sex offender.