I always thought that the moms weren't suppose to throw the showers since they are paying for the weddings.
As an Aunt, I threw the shower for my neice. My sisters and I did it together since no one else was going to do it.
It's proper for the bride's parents to pay for the wedding but the maid of honor is suppose to host the shower.If they host a bachlorette party instead then I think either the mother in law or mother to step up and do it.It doesn't need to be lavish and overdone.
I had 2 showers.One was from my coworkers.She was also my maid of honor.She threw one at work and even the male managers and guy friends of mine came.It was nice.They did the same for my baby shower.I loved it.
My mom also threw a bridal shower for me.That was the larger one with family that wasn't invited to the wedding reception due to not having space and more money for it.