Prudie skipped over some very big issues with the gentleman that was trying to spice up his marriage. Not only did the wife rub his nose in the fact that she had been more adventurous with previous lovers, she insulted him for not having been as creative before he met her. This is emotional bullying. These include subtle digs at his lovemaking prowess (just because something was bad with a past lover doesn't mean it will be bad with the current lover.)
This woman needs counseling, and not just for the sex issues. The man is trying to find ways to address issues in the marriage that are important to him. He doesn't seem to be wanting to go to any crazy extremes. If she doesn't feel comfortable doing these things, just say so, there is no reason to revive her past liasons as part of her answer.
How would she feel if she wanted a massage and he said no, he used to give them to his old girlfriend and it wasn't any fun. Her answer shows a selfishness. It doesn't seem to be about having sex, the husband specifically states that he isn't complaining about the number of times they have sex. It is about where and how they have sex. This is a control issue. She doesn't offer suggestions for spicing up things, she just says no, and insults him, even though he has made it clear this is important to him.
They need to find out why she needs to frame her answers in this way, whether he has done something to make her defensive, or whether she has other factors that make her act this way.