I know that bras and panties are lingerie; however, is this appopriate? - I am hosting a lingerie bridal shower and the bride-to-be has requested bras and panties. She even insisted that her sizes be included with the invitation, along with websites that sell her preferred underwear.
You can certainly list the theme for the shower but asking for specific items and telling the guests where to buy them isn't appropriate. Gifts are to be selected by the giver, not the recipient. If she doesn't like what she received she can return the gift to the store. Of course, she will not tell the giver but will send a heart-felt thank you note. The note will be heart-felt because she should be thankful that the guest took the time to select a gift and to attend the shower.
Hopefully you can convince the bride. If not, you can opt out of hosting. No one is obligated to throw a shower. Top Wedding Questions Forum Moderator - "Write your sorrows in the sand, your blessings in stone".