When my DD was that age we used to put colief in all her bottles and used infacol too as she was really gassy and couldn't seem to get her wind up very well. She took a loooooot of burping after each feed and we couldn't lay her down for a while after a feed or she'd get upset too.
We don't completely ff but she gets her bm in a bottle too and we added the colief to that as well. We went from slow flow teats to medium flow at 3 weeks old because she was collapsing the teat from sucking so hard to get the milk out fast enough.
We use SMA and were considering switching to SMA comfort, but we just stuck with the colief as it seemed to work. We use tommee tippee bottles, we did try the munchkin latch and medela calma ones but DD didn't like them.
Because of the colief I didn't make my bottles up fresh when needed, I batch-made them the night before and they stayed in the fridge til they were needed, as the colief needs a while to work on the lactose. I stopped the colief at 12 weeks, but I still batch make her bottles now and DD is nearly 11 months and has never suffered for it
The HV might be able to offer some suggestions on what to do...change of brand, infacol, colief, change of bottle...all things to consider.
ETA if your friend decides on colief, get her to ask the gp for it on prescription...a tiny bottle costs £11 and it only lasted us 5-6 days!