The problem may be poorly fitting muffs. My wife complained about the noise while shooting and we finally figured out that the muffs were not providing an airtight seal around her ears and therefore weren't blocking very much sound at all.
We did some testing and found a good quality of muffs that fit her properly and she hasn't had any problems since.
...they "pass-through" additional noise like speech, non-stop.
There may be some muffs like this but I've never encountered them. The ones I've tested stop passing all noise anytime there's a loud enough noise to cause the amplifier to cut off and they will keep "blocking" the sound until the noise level falls to an acceptable level.
So you hear normal speech until a shot occurs. The shot and the speech (all the sound going through the amplifier at the time) will be cut off and prevented from reaching the ear. Then when the circuitry decides that the sound level is acceptable it will begin passing sound again.
I remembered how I cant shoot a long rifle with big muffs, and decided I'll save $100 and stick to my earplugs.
Earplugs will definitely help, but there is significant sound transmission to the inner ear via the bones surrounding the ear. If you want to appreciably deaden that sound you will need to use muffs. Muffs AND plugs are a good idea, but if you're going to go with just one method muffs alone will provide superior protection compared to plugs alone.
By the way, you can improve the fit/seal (and also the comfort) of a good pair of muffs by retrofitting them with gel pads to replace the foam pads that normally come standard.