Mother in law suggests formula...

Hi,

My mother in law suggests formula for my baby at night so that he and I will sleep longer. He is mostly a breastfed baby, but a month ago I had to supplement 4-6 oz of formula per day due to clogged milk ducts and my supply dropping. We are down to 2oz-0oz of formula per day now, but she keeps harping that we should give formula to him at night.

(She gave my husband cereal in his bottle at one month old to "help" him sleep longer. He was strictly formula fed as she had no desire to breastfeed).

Any talking points for her advice that I should give him formula at night? Because it's kind of annoying me...