Samantha's background was left intentionally vague, so there's no official data about her.
SPOILER WARNING (since the spoiler tag seems to have gone away)
Pretty much the only way the runners would ever find out about Samantha's background is by taking and reading Nick Ryder's Lone Star case file on her abduction (or mind probing Ryder), and even Ryder doesn't know what Janus did to her. Even Samantha doesn't know anything about her background. She's spent 20 of her 26 years between medical tanks and operating theaters, so she knows pretty much only what she's learned since she escaped. And Remo would have all but demolished the research area of the Janus host while busting Samantha out, so there's nothing to find on her in the host.
That being said...and this is just how I thought of her (lesson to learn as I hope to keep writing--write down this stuff!), so take it with the appropriate container of salt:
As I envisioned her when I wrote the mission, Samantha was an otaku, rolled up (kidnapped) as soon as someone noticed her gift. Janus did more genetic experimentation (trying to reproduce her gift) than anything else. Looking at her stat block, you'll notice that all of her augmentations are delta-grade bioware. I had envisioned these (fluff-wise) as unintentional results of massive genetic modification, but there are no rules for that in SR5 so that's how I statted things out.
Her childhood "imaginary friend," Remo, became a sprite over the years, and then eventually became a free sprite during Janus' experimentations on Samantha. His relationship with her is likely what kept them both from going completely insane after what she's gone through and what he's watched Janus' doctors do to her. As Remo grew in power, he eventually became powerful enough to crack the host.