Answer:
No , Jessica Rabbit was faithful to Roger Rabbit ; her alleged infidelity was simply a plot device used in the film to develop the characters and the narrative .
I say, can you honestly trust a suspect? Hell no! She claimed that it was part of a plot but who can you trust? Even if this plot were true (which it might have been) she may be guilty for part of the crime of framing Roger Rabbit. She once dated Reader Rabbit, and he is now among the missing list.