She obviously has never used it or has no idea and is thinking of milk as soon as the word lactose is heard (which mind you I thought initially too)
I just bottled my Lemonade which had 500g of Lactose added and it is not milky or creamy, no where near it!!
It is actually clearing quite well, it will remain cloudy but no milk or cream tastes or looks.
I also (as a experiment
) added 200g to a coopers lager recipe I did and I just bottled this morning, sweeter taste but it is quite clear!
If you search up there are some threads on this site as well as others regarding its use, apparently it can be quite sweet as it us unfermentable (mostly) so dont add to much!