Not entirely rubbish, but very exaggerrated.
No baby should have soya formula unless it has been prescribed by a properly qualified dietitian or paediatrician.
Her baby is unlikely to be really lactose intolerant, as lactose is in breastmilk, and true LI babies cannot even have breastmilk for this reason.
Mild and temporary LI, after a bout of gastroenteritis, is possible and is best treated in most cases with breastfeeding, which repairs the gut.
Soya formula contains hormones called phyto-oestrogens which have led experts to be concerned about the effect on a baby's development, especially baby boys.This is however speculative,
Yet it is not really sensible to give soya formula unless the baby really can't be nourished any other way.
This baby needs a proper diagnosis of his feeding problems. If his weight is causing concern then bf can be improved - if she is really keen on topping up, for some reason, she can use expressed breastmilk or regular non-soya formula (unless, as I say, someone qualified reckons the risks are outweighed by the benefits).
Hope this helps!
She can check out soya formula herself by googling for its risks.