I think she really thought that pattern was the Soul of her mother. My english is not that good but I thought i read something like that at the Point when her father wanted to hit her. So she realized that pattern was not her mothers Soul when jasnah (dont know how the Name is spelled i heard to the audiobook) knew of this creatures as spren. It also makes sense because the Moment she first met with pattern was when she killed her mother. Syl didnt die this is said also she just lost her consciousness, when kaldin fell into the chasm cause he wasnt thinking about the others and how to rescue them but thinking about his own importance and that a big godlike Person like him cant die that inglorious way. I mean syl said he is the only Person on Roshar who attracted a honour spren i think that requires honorable thinking even when youre near death ( you know "I cant die I am the storm" and things like that.