It sounds more like she wants to do them for his pleasure despite the discomfort, and doesn't want to tell him because him knowing it's uncomfortable would be a turn-off for him. There's nothing wrong with experiencing discomfort during sex if the person experiencing it judges the discomfort is worth the benefits.

For example, many women with conditions such as vaginismus experience significant pain during normal intercourse but choose to have intercourse anyway because they still find certain aspects of it pleasurable and/or emotionally significant. Are these women obligated to tell their partners every time sex is painful, therefore possibly killing the mood, even though they themselves want to continue having sex?