Yeah. After the victim died from the suffocation they had inflicted, the victim only had some small cuts and bangs to the body. She wasn't heavily bloodied up, so her body is presumably very much intact as the normal self. So, if these two suspects were really sick and deranged enough, they could have done something sexual. Obviously they dismembered the victim, so we know they are deranged enough in the mind to possibly go there.
I'm on the fence about whether the male suspect would have done it, if that were the case. I think it might have been possible, but judging from the interview, he seems to have some form of PTSD about the whole experience. So I don't know whether he would have done it, though I suppose it could have been possible if he was 'in the moment'.
We don't know if the female suspect is guilty. But if she really was guilty all along, and judging by the way she acts so calmly and nonchalantly right now, she will come off as a cold calculating psychopath. If that were the case, add onto the fact she had a sexual fantasy, I think it could have been possible she would have done something sexual.
All speculation anyway, since there are no forensic details suggesting anything had been done, although you could never prove or disprove whether the suspects simply felt up the victim. But, I think a person capable of dismembering someone of whom they had a sexual fantasy of, and for which the crime had a sexual motive, is probably capable of some degree of necrophilia or other sexual indecencies to the body, especially as you say, the theory is they were just going to kidnap the victim to do stuff to at a different location. Except, now the victim is lifeless. But that is not to say they will "pass up the chance" anyway, if they were really deranged.