Research for the novel leads to characters taking over

I am loving the research for the book. All my favourite subjects: history of Elizabethan households; poetry (female Elizabethan poets - very rare); chemistry, including the transition elements; and a fair dose of archaeology and anthropology thrown in. Thank goodness for the search engine of the university library! Today I have looked up the naturally occurring incidence of Thorium, the poet Isabella Whitney and bellarmine jugs and other Tudor pottery. I did manage to get my 1000 words written as well, and have wrestled with pen and paper to make sense of all the threads uncoiling and rambling through the story. How do murder mystery writers cope!

I have a tendency to be surprised by my characters. Today, I found a perfectly pleasant young woman who has helped the plot, and the main character along, is going to fall down the well she has just helped excavate. I just hope she survives. Is this just me? I thought I was in charge of my own creations but once I build them and put them in entirely fictitious circumstances, they take charge and do odd things.

Take Jack, principal character in Borrowed Time. Since I was thinking about my creative choices for my dissertation, I wasn't expecting her to turn up in it, sit down in the rocking chair, and start reading book titles. I'm going to have to give in and complete that interview, because she would like to know why I didn't make Sadie the central character, allowing her to hug the shadows, where she prefers to be.

So I'm wondering: is this normal? Am I just facilitating these characters' stories or am I actually in charge?