Elvie Catcher and Foremilk

I just started using Elvie catcher and noticed that the leak that is caught is much mofe waterier than the milk I express using a pump. Quick googling provided it's because the leak is mostly foremilk.

My understanding is that foremilk is high in lactose and too much can cause upset stomach for the baby. So is it worth to continue to use the catcher? and if so, how should I provide the foremilk to my baby? On its own or mix with pumped milk that is fattier?

Thank you.