The sentence that does not maintain a consistent point of view is 4. Shelley thought about what to buy. I was out of money and had to call my mom.
The point of view is the narrator or the person about whom the information refers to. In sentence four, Shelley is mentioned first and then it changes the focus to the first person singular "I".
The other options are consistent because option 1 is told from the first person singular "I", option 2 is told from the point of view of Shelley and option 3 is told from the point of view of Sam.
