She's not in a secure unit because she is not considered to be a danger to anyone else.
She killed her daughter because she intended to kill herself and didn't want to leave her behind, she did not attempt suicide because she had killed her daughter. It's called extended suicide apparently.
There is no particular opinion of mine attached to this, it's just driving me nuts reading people asking questions about this, or making assumptions when it's all in the article, then other people who read the thread and not the article picking up the misconceptions and running with it. 
If I had to add an opinion I would just say it is very, very sad all round. It must be horrific to find out you did something like that (it also says she can't remember doing that, maybe that is a blessing for her) and have to live with it forever (it also says she was a doting mother), but those are the consequences of doing something so terrible. 