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If the benadryl has not helped in the time since you've given it, I would take her to the ER. The risk of her having a reaction to something that could cause major issues for her and the puppies is high. When you take mom, go ahead and take the puppies with her so that they can be evaluated as well.
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I would find a vet this evening and go now. Two things we're worried about here: retained babies, placentas, etc. can cause an infection and mom can become critical quickly, and (2) a true allergic reaction.
This could be a life threatening concern for her. If she were my companion, I would not delay. I would see a vet this evening and not wait for Monday morning.