My 2 week old gets phlegm on her chest after drinking her bottle. she's on nan optimum. is she perhaps lactose intolerant?

Doubt it: Most congestion & phlegm buildup at that age is due to irritants. Dust, fragrance, perfumes, etc. all are not handled well by a baby with a narrow nasal passage to begin with. They try to flush these irritants with mucous & create more & the mucous lines their nasal passages creating congestion, cough, rattle. A good nasal cleanout with saline helps but eliminating airborne irritants helps more