I'd actually like to see Yamada mature in college. I can see her feeling a bit inadequate when using Kase-san as a yardstick, since she's smokin'! But she's studying something she loves, receiving support from that outstanding woman, and presumably making friends with other students who share her interests, rather than the fairly random assortment of people you find in high school.
Kase knows how pretty Yamada can be.
I actually think Yamada has matured alot since the start of the series. Things that would make her a wreck at the start she handles in stride and accepts now. She stood up to her parents about wanting go to college in tokyo. She did the move completely on her own where before she was kind of helpless without her friend. Plus she just carries herself in a more confident/calm matter in the last couple chapters. She still has issues and a childish side but she has definatly matured.
One thing I never got is at the beginning of the series Yamada is portrayed as being dumb/slow and plain. But in reality she is smart enough to get into a good college. She has a rather good body with curves. Top it off she is fashion oriented with good fashion sense and likes to dress up when out of her school uniform. Hell she even has a thing for wearing fancy and lacey underwear.
