Confusion over minor roles - Help please

I have read a whole lot of reviews of this film, gone through the IMDB cast listing, and read all the threads on this board and I am still confused about the non-credited actresses.

Roxana Nieto is listed as the first victim but the first victim is the skateboard girl played by our very own colleague jodancer. So is Roxana the pool victim? If so who does Cristina Cottrelli play?

Everyone seems to agree that Leticia Marfil plays the tennis player who gets slashed in the bathroom although the cast list has her as Mary the elevator victim. She is called Suzy by Kendall and therefore should be the same girl who asks the Prof about "pectorals" as she is called Susan by one of her friends.

Silvia Gambino is listed also as Mary the elevator victim. This seems to be correct as Gambino was only 17 at the time and so would not have been allowed to show skin. Comparing her with later photos of Gambino there is a resemblance but it is hard to confirm this.

Having just watched Night of the Werewolf I think Pilar Alcon is the model in the puzzle not the girl in bed with Kendall (the gag me girl). No idea who she is. Maybe she is Carmen Aguado as Carla the gymn instructress she is credited as in the IMDB list is basically a non speaking part.

There is a scene just after Isabel Luque (as the reporter) is killed on the water bed where the slasher goes into the cold room and there is a naked female body seen hanging up. This body is not the same as the one at the end (its arm is not sewn on). I think this is meant to be the reporter but can't be sure.

Any help please to try and confirm some of these.