i'm sure hayley said this because she was so impressed with her mother's intellectual wisdom... and thought there was no way her mom could have learned all the wise ways of the world in less than 30 years. i'm sure that's it.
If you think about it, Hayley's height makes her look 2 years older than she is. Perhaps this has skewed her ability to judge ages of adults. The woman who colors my hair asked me how old I thought she was, I asked her to please not ask me that because I'd be way, way off. I do not judge age well at all. She forced me, so I guessed she was 42. Nope, she said she's 31. I warned her!