Yes, great advice and I totally agree. Also, she might listen to you if you tell her that there was no way it was lactose intolerance (babies just don't get this, it is extremely rare and if they had it they wouldn't be able to tolerate any bm or formula from birth), but she might read an article on the subject. The link below explains that babies don't have lactose intolerance and gives some information on what is usually going on and how to make it better: Australian Breastfeeding Association - Lactose intolerance and the breastfed baby. Hopefully having some extra information will help her.

It's so great that you are trying to make things easier for her