Anne,
It sounds like the baby is having trouble staying connected, so maybe if mom
uses football hold with good neck and shoulder support , using hand that is one
same side as the baby is feeding on, and with the other hand  holding the breast
, compressing to a sandwich shape, and exerting a slightly forward position
towards the baby's mouth to help the baby keep the breast in place.  Then when
the baby gets tired and takes time to get her breath, she won't automatically
lose the breast.  The idea of letting the other child take some of the foremilk
makes sense, and the baby will get more hind milk that way.  As she gets more
adept at breastfeeding and can maintain the latch longer, it should get easier.
I would suggest lots of skin to skin holding with this mom and baby as well.
Kangaroo care.  The warmth of the moms skin on her tummy will feel good if she
is having colic symptoms.  Hope this helps.

Ann Calandro, RNC, IBCLC