Try these:
*Feeding without a shield while baby is asleep. (works better if baby is
used to sleeping near mum)
*Trying second side without a shield, alternate sides to build up supply
*If attachment without shield is still a big problem (not just
like/dislike) then keep feeding with shield, build up supply with pumping,
etc. and KEEP TRYING - eventually baby will be big enough to accept nipple
without shield.
*Explain that mum can supplement with pumped breastmilk -
doesn't need to be formula.
*Does mum sterilise shields in solutions? Wiping sterilising solution on
nipples so they smell the same as the shields may help...well you said ANY
ideas!
Good luck,
Querida, Australia