Ty: Yay! Love gardening kiddies :3 Lani would definitely frequent Ty's workplace. She might've of heard about the occurrence from word-of-mouth, but she isn't one to judge (even if she sees it as the accepted norm, it goes against her natural neutrality to believe someone inherently did wrong). She loves having people around her that she can share her passions with, and her gardening habits help to create the relatively zen personality she's got going on. I reckon they'd get along friendly, for sure!
As for Juniper, I agree. Aside from both being seniors, they wouldn't really coexist.
Caedyn: Caedyn has quite a strong presence, which totally eclipses Lani's conversational pacifism. An interesting relationship could come out of the social media thing; I feel like the pair would get along online, because it hides the parts of people that you mightn't necessarily want others to see. If their relationship was born online, and then the meet in person, things might flip on its head. This would let Caedyn enact her chaotic duties, and Lani needs a little more hate in her life; she's too stable. So, yeah; possibly were friends online but once they met each other they were like "nope, I'm out."
Juniper's chaotic in a sense, but not quite on Caedyn's level (I don't think anyone else could be), but there's enough appeal to the relationship that'd help Juniper put up with anything she didn't quite agree with. Bonding over theatre and the whole "fuck relationships" vibe would be enough to cement a friendship, and Juniper would probably feel comfortable confiding in Caedyn about her problems with her past relationships because they share a history of poor partners. She'd also give Caedyn props everytime she scores, so there's that ^.^
Abby: An acquaintanceship or at least knowledge of one another would fit best between Abby and Lani, yeah! Abby is a wonderful person, so I know that Lani would have at least heard about her efforts to better the world. There'd be no malice or anything negative between the pair; I agree that they're just too apart to have anything more than a casual "Oh haaaaeeeeee, you look greattttttt."
Timelines are a pain >.< I love the idea of the duets and playdates; if Rick and Abby are a recent thing, I can say that Juniper's been single for six months-ish (assuming junior finals were June 2014, and pregame is set roughly at the beginning of January 2015), so if they've been together for less than six months, there could've been something going on between the pair. An alternative would be sometime in freshman year, when Juniper would've been recently out and before the commencement of her relationship with the nonexistent Jay. Juniper can be an awkward person (as seen by her recent cafeteria antics), but she'd still be chill with Abby regardless, and would still definitely want to hang out with her and her cats :3 I propose a pretty solid friendship, with some sort of past involvement if you want Abby to be a lil' queer :3
Isaac: His poor reputation would make Lani feel awkward around him, because it's generally what she prides herself on (she tolerates others with poor reputations when there's a lack of malice between the pair). His antagonistic nature would probably annoy Lani; she'd probably actively avoid him through a surface-level dislike.
I detect a rather strong distaste for Isaac in Juniper's mouth. His attitude would irritate her to the moon and back, so it looks like there's a relatively mutual hatred forming here. Juniper, being the stubborn and persistent person she is, would equally vocalise her feelings about Isaac, which could create some very, very interesting screaming matches. Also, there's that connection with Oskar going on and...yeah. Yaaaaaaas enemies!!!
Okay, brain fart complete. Thanks for the suggestions and the cannon of friends/enemies/kiddies Ducky! Let me know what you think and I'll start adding Ty, Abby, Caedyn, and Isaac to the relationship lists :)