Yes, YTA. Your toddler is just being a little shit like all toddlers do. It doesn't sound like your wife is neglecting your children. You are there to watch them. The kids are just getting used to a switch - more dad-time than mom-time, and toddlers act out at any change. It doesn't mean the change is bad and has to be reverted.

You certainly can mention to her that the 3yr old misses her and, in a positive way, suggest to her that maybe when she gets home, she spends a dedicated amount of time just her and the 3yr old while you care for the 1yr old, like reading a book together or something. But asking her to stop caring for her dying mother because your toddler is acting like a toddler would make you TA.