Is Mary the Magdalene explicitly called "a great sinner" by an Evangelist or any other character in the Gospels? No, but here's a helpful tidbit:
there's more than one way to say something. And, fortunately for me, your unwillingness to accept or inability to understand the way in which it is said in Scripture that Mary the Magdalene was a great sinner still bears no effect on the following point:
Only two of the five women who have anointed Jesus, the well-known repentant prostitute, and Mary the Magdalene, from whom Jesus cast out seven demons, anointed Jesus with expensive ointment using their hair in Bethany. Again, why are those details insufficient reasons to deduce that they were the same woman?
Again, Jesus cast out seven demons from Mary the Magdalene whom they had possessed (
Lk. 8:1-2). Do demonic spirits of Satan influence and control a person to commit moral or immoral behavior?
Again, why do you believe it to have been possible that the seven demons Jesus cast out of Mary the Magdalene were a severe case of PMS when there is no scriptural evidence to support that, and you only accept as true what is indicated in Scripture? And, again, would the casting out of PMS from Mary the Magdalene have been a one-time or monthly event?
If Scripture indicated that Mary the Magdalene was wholly moral in body and spirit from birth to death,
then you could say that there's nothing in Scripture to suggest or say that she never committed prostitution, or any other sin. But, you can't, at least not without being intellectually dishonest,
because by your own admission, you believe that she did commit sins, despite also believing that there is no indication in Scripture that she sinned, nor of how she sinned, and thus there's no type of sinful (immoral) behavior that she could've committed, such as, for example, prostitution, that is off the table for discussion.
I have too much conviction to depart from this discussion, but to each their own.