Sec. 43.02. PROSTITUTION. (a) A person commits an offense if he knowingly:
(1) offers to engage, agrees to engage, or engages in sexual conduct for a fee; or
(2) solicits another in a public place to engage with him in sexual conduct for hire.
(b) An offense is established under Subsection (a)(1) whether the actor is to receive or pay a fee. An offense is established under Subsection (a)(2) whether the actor solicits a person to hire him or offers to hire the person solicited.
(c) An offense under this section is a Class B misdemeanor, unless the actor has previously been convicted one or two times of an offense under this section, in which event it is a Class A misdemeanor. If the actor has previously been convicted three or more times of an offense under this section, the offense is a state jail felony.
(d) It is a defense to prosecution under this section that the actor engaged in the conduct that constitutes the offense because the actor was the victim of conduct that constitutes an offense under Section 20A.02.
Sec. 43.01. DEFINITIONS. In this subchapter:
(2) "Prostitution" means the offense defined in Section 43.02.
(3) "Sexual contact" means any touching of the anus, breast, or any part of the genitals of another person with intent to arouse or gratify the sexual desire of any person.
(4) "Sexual conduct" includes deviate sexual intercourse, sexual contact, and sexual intercourse.
So, at least in Texas, it depends on 1) whether you touch her breast; 2) whether the touching is "with intent to arouse or gratify the sexual desire of any person"; and 3) whether a fee is paid.
http://www.statutes.legis.state.tx.u.../htm/PE.43.htm