My cousin and bm asked if she could bring two friends: and she can pay for them.

Yes I think so. But if I am asking a close person to be my bridesmaid or to attend to my wedding whatsoever, I will also do everything to make this person feel comfy. Of course it depends by the person. If it was me, i'd panic at an event full of strangers. Especially knowing that brides and groom won't have much time for me!

I do use it a lot in my life. As Michelle said, "no is a complete sentence".

This is very bizarre and frankly a bit rude. It's sweet that your cousin wants to allow her friends an opportunity to travel outside the country, but take another trip for that. Has she thought about how uncomfortable it might be not just for you, but for them, to go to a complete stranger's wedding? Weddings are not weekend party mixers where you can bring just anybody along and hope they click with someone. If her husband couldn't make it, and she wanted to bring a friend in his place as a plus one, that would be entirely different, not to mention okay. It's common courtesy that bridal party members are allowed a plus one. This, however, is a no-go. You need to tell her ASAP that the only plus one she's allowed to bring is her husband. If she puts up a fuss, tell her you don't know these people and aren't comfortable having total strangers at YOUR wedding. Maybe have a backup bridesmaid on call, too, just in case.

Its not only about the extra two people. You would also have to see where they would sit and most likely re-arrange tables. Probably add a table which will be more money for flower arrangements. She is a cousin so she should know most of the other guest.