The rape shield provisions usually preclude questioning the alleged victim about sexual activity with people other than the accused. I generally don't have a problem with that. To take an extreme case, suppose a woman willingly had sex with ten different men in the 24 hours before the accused is alleged to have sexually assaulted her; the activity with the other men is not evidence that she consented to sex with the accused, and is rightfully excluded. Also, evidence that a woman consented to sex with the accused on Thursday is usually not admissible if the accusation is assault on Friday. On the other hand, if the victim had consensual sex with the accused AFTER the alleged assault, that is usually relevant and will generally be admitted.

The result is that an extremely explicit sext from the alleged victim to somebody other than the accused will almost certainly be inadmissible; the same sext addressed to the accused probably will be admitted.