Cerie never realized how hung up she was on Kenneth until Hazel snatched him up.
It wasn't even completely about her own feelings. Hazel seemed like she was a really awful girlfriend. Whenever Cerie saw the two of them together, it was usually Kenneth talking a mile a minute and Hazel not even pretending to listen. But Kenneth was too happy to have someone by his side to notice that Hazel didn't care at all. She didn't even know his name. Cerie might not have always understood what Kenneth was talking about, but she was at least a decent enough person to actually listen to him.
Hazel was also a sad reminder of why she never ended up with Kenneth in the first place. The two of them came from different worlds. Kenneth seemed to have more things in common with Hazel. They both liked all these old TV shows that Cerie had never heard of. Plus, Hazel was a page, a position that Kenneth held so much devotion toward. Maybe it was the world's way of telling her to not even bother anymore. Kenneth deserved someone more on his level that could make him happy, and she was destined to be rich guys with a pretty face but no personality for the rest of her life.