Our Pearl is neurotic, hates food, looks down on humans, occupied by her career, and probably not into men. Assuming we get past the last part, that still leaves everything else to contend with. She's a good character, but probably not a good person to seek a relationship with.
Yellow Pearl is smug, bitchy, and obsessed with someone else. Based on the modelling thing, she'd probably be easy to flatter, but difficult to truly please. Seems like the demanding type, but that's more me applying stereotypes based on what else I know about her.
Bloople looks like the easy answer, being the cute, shy type, but she has the same Diamond obsession as Yellow, and based on her art, might not care for organics, or people she deems "lesser". Not much else is known, so she's a bit of a wild card.
I'd say Our Pearl, but only because I'm familiar with her, and know what egg shells to avoid stepping on. Definitely keeping it as a one time thing, frame it as practice for when she finds the motorcycle girl.