If your DD doesn't take care of them then she has to give them up. Harsh maybe but I would expect an 11 year old to be fully capable to care for a guinea pig.
At that age my siblings & I were expected to feed, water & clean up after our pets (& we had several being on farm).
Might be time to follow through - if loss of privileges etc isn't working. Maybe sit her down & give one last warning - either she takes care of her pet or she must rehome it.
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