Cherry Cheesecake is only four, but she’s no steeplechaser. She’s had 6 starts in SC, and hasn’t earned a dime. I can keep experimenting with equipment, but I also think SC is just not her own thing. Ideally I’d like her to hit champion status before joining the broodmare band, but she hasn’t hit the board since July (top three not since June). Do you think I should keep trying with her, or retire?
Retire her. 
She’s never been a consistent pony, unfortunately. If you have the money to keep playing with her until the end of her 4yo career, then by all means do so, but I don’t think achieving Ch. status is in her cards… if you continue to race her, I would do it intermittently, so at least if she manages to pick up some money you haven’t wasted more than you think it was worth. 
Don’t forget also that Ch. status does not a Gold-ranking mare make. 
It might up her asking price if you sell her, but that would be it until her foals hit the track and you see what she’s like as a mama!
Oh, I know champion doesn’t = gold. I’ve got enough mares telling me that already, haha (and enough Ch.+ mares telling me they’ve done enough work on the track so their broodmare careers can now be lackluster at best). I just try to get mares to Ch. nowadays before putting them in the band, but I like her lines enough to just keep her. She’ll probably be retired, thanks! I think I just needed to hear it from someone else.