Not a dad, but at five years old, she should be able to take a bath by herself. Run the water for a reasonable temperature and let her do the washing of her body, etc. Obviously she needs to be taught how but she can do it herself. If her hair is on the longer side, then perhaps a shower would be best so she can wash her hair more effectively. Her doing these things herself will help support her own independence/self reliance/responsibility and teach her modesty and privacy. It eliminates either of you from being accused of anything improper. An adult turning the water on and adjusting the temperature is reasonable, but after that she should be able to undress, bathe/shower, dry off and get dressed on her own. The hair combing and drying may still require some assistance, though, for a couple more years.

Also, be sure your wife gets some "her" time where she can indulge in things outside of "Mom LIfe" since y'all are parenting round two after thinking you would be enjoying life as empty nesters at this point.

But, after what you have posted here, it does seem like your wife needs to figure out how to accept the fact that this little girl child is a wholly different creature than your son and that she cannot expect her to react the same as your son did. It may be as simple as changing tone or delivery of whatever it is that she wants done.

As others have mentioned, being consistent in both bed time and the routine leading to it are key.