Ok "boys", just a few things you should know...
1) get a towel down, preferably a red or dark one.
2) probably better leave the cork in, even if you fuck her. Or not, depends on the woman, and which day she's on.
3) I don't recommend saying "That's OK, I'll just fuck you in the ass". It's totally logical and somehow that bothers women
4) I *DO* recommend saying, "Orgasms will help reduce your pain and shorten your period." (one's iffy the other is kinda a lie, but seems to work)
5) Go ahead and offer to "do other stuff", especially if you get blown and she gets some (external) finger action.

Remember, you want sex? Man up and do it!

I think she looks pretty sexy even with the string

pictures of ladies with tampon strings showing are not only not pretty or sexy but are downright gross

I do believe it's her time of the month. Pull the rip cord and let's go.