One year-old attention spans are not still waters, nor do they run deep. That is why the simplest of imitative and repetitive actions, like pretending to nod and talk along while mother is on the phone, often emerge around the age of 12 or 13 months.
Evolving from the simple to the complex, pretend play unfolds in a succession of events. The older infant (second half of first year) has sufficient memory and brain development to keep track of objects and current events. Emphasis on “current.”
The information (actions of other household members like folding towels, or stirring) is readily available, and tools are, as well. At first, the accuracy of the prop matters — she thinks the best way to imitate your telephone conversation is by taking your real phone out of your real purse, and dialing!