Answer:
"better-than-average" effect
Step-by-step explanation:
The "better-than-average" effect causes a person to think of themselves as better than others. This type of thinking is generally more prominent when the person is among their peers.
Here, when Tanja is with her friend she thinks that she is better than them. But when she notices a an old lady struggling to cross the road, she takes little notice. Here, her peers are not with her.
Hence, this tendency of hers is explained by the "better-than-average" effect.