Alrighty then, I figured I'd get around to listing possible relationships Syra has with other characters. Let's see here...
Well, Videospirit already agreed that Syra could've visited Chi and the nymph's grove and they awakened her sexual appetite, fun stuff.
Syra could be acquainted with the centaur just from hanging around the same environment, especially if he hangs around Chi and the nymphs too. She could also know Alice through him.
Aside from what I suggested above, Syra and Alice could've met if they were in the same area and their interests (protect nature and defeat evil, respectively) aligned on an adventure.
As for Hart and Syra, I'd actually prefer if they didn't meet after Syra meets Chi and the nymphs. I have ideas for that. They could've met before that, while wandering, but Syra wouldn't have understood Hart's advances very well.
There's not much information about Aio's wanderings after leaving his tower, so I'm not sure how he could've met Syra.
Syra and Garret could've partnered up in the past once or twice, as I think their morality is fairly similar, though Syra's is more primitive, revolving around fairness and hurting others only if necessary to survive.
Syra and Dornal are less likely to have met, unless his vigilantism drove him to put down some corrupt thing or another, and Syra did the same.
Syra's not a big fan of slavery, as one might imagine, so any interaction she would've had with Nys probably wasn't friendly. Still, it's entirely possible their paths could've crossed before.