Yes, Singed does chemicals. Some chemicals can cause pain. Pain can cause psychological trauma.
"Prepared subject for implantation. Tested a surgical technique I observed during the Ionian Campaign to reach the scapulae. Required several minutes of drilling through bone to attach the alchemical chamber and pumps that will deliver the transmutative formula. Subject wailed and pleaded. Insisted he was no longer a monster, but a good man. Ignored the distractions and threaded lengths of delicate hoses throughout his extremities, splicing them with his veins and arteries. The subject remained conscious and screaming for six hours. Very encouraging as he endured significantly longer than earlier failures. Finished by integrating the mechanical augmentations with the neurolous fibers of the spine. Minimal stitching required. Subject stable and recovering. I must rest and replenish before tomorrow’s procedure."
This is from "engineering the nightmare". Shit like this would definitely bring with it some mental issues.
Personally, I think Singed did experiment on her. As for how and why, I'm unsure. I don't doubt that I'm wrong, but I think it would be an interesting story. Having her connected to both Warwick and Singed in my mind has the potential for some entertaining and fucked up situations.
I love your headcanon, by the way. I think it's the most likely possibility for her connection with WW. Also, it doesn't rule out the possibility that she was experimented on. :p