From the SCC in the Ewanchuk case: "The absence of consent, however, is purely subjective and determined by reference to the complainant’s subjective internal state of mind towards the touching, at the time it occurred.  While the complainant’s testimony is the only source of direct evidence as to her state of mind, credibility must still be assessed by the trier of fact in light of all the evidence.  It is open to the accused to claim that the complainant’s words and actions, before and during the incident, raise a reasonable doubt against her assertion that she, in her mind, did not want the sexual touching to take place."

What is in the victim's mind is indeed part of the analysis but, as I've stated already, messages that pertain to the determination should be admissible. That does not mean that any and all text messages between the victim and the accused ought to be admitted.