EXactly! "Early stages" meaning she would have no doubt felt tired.
I know there may be some people who find discussing mentruation embarrassing but it's a fact of life and imo needs to be discussed.
If there were little specks of blood on Sheila's foot. I don't believe they were. They could have been from when she changed her tampon. Bit like when you have a nose bleed.
In the Nick Rose murder case, he argued that the spots of blood found in his car, could have come from his victims nose after she allegedly snorted cocaine.