Indispensable but Unimportant?

"The presence of woman is an indispensable element of spectacle in normal narrative film, yet her visual presence tends to work against the development of a story line, to freeze the flow of action in moments of erotic contemplation" (Mulvey, 837).

After first reading this, I thought it made no sense at all. Mulvey is saying that it is necessary for a woman to be in "normal narrative film", which is an interesting point, but she then goes on to say that a woman's presence "work[s] against the development of a story line". Why, if a woman's presence hinders the development of the film, is her presence so ''indispensable"? It seems to me that in trying to make a valid point, she is contradicting herself. The point when I thought that what she was saying went from confusing to ridiculous was when she decided to quote another person to prove that woman's presence is necessary. She chose to quote Budd Boetticher who said: "What counts is what the heroine provokes ... In herself the woman has not the slightest importance". For some reason, this doesn't seem to support what she said before. If woman is so necessary, why on earth chose a quote saying that "woman has not the slightest importance"? Admittedly, I may not have understood other things Mulvey discussed, but I honestly do not believe that she chose her quote wisely.