Sheridan Smith - Botox?

I'm just half way through watching the first episode, & I'm distracted the whole time by the lack of facial expression by Sheridan Smith. For a woman that has just found out her husband has been murdered, & that he was leading a double life she's hardly showed any emotion. She hasn't shown much grief or anger, & looks like she's sort of smiling a lot. It's really weird. Also the filming often is really close up to her face in group scenes. I guess this might be to show a sense of the oppressive emotions but while her face looks blank it's really strange.
I normally really like her in stuff but this is really off putting. Maybe it'll turn out her character is having some sort of catatonic breakdown