How can I possibly know whether she is turning to the right or left without context? I'm confused.
You got the drop-down box which include à "droite" and à "gauches". There is no "gauches". "À droite" = to the right. "À gauche" (not à gaucheS) = to the left.
If you read the comment two messages below your one by EthanTown it will answer your question and give you the ways this is said in English.
tourne is an action or something that is still happening. Is turning is different from has turned or turned
That's simply the way it is. The only situation where there would be an article is when you specify "at the right hand side of something or someone", «à la droite de quelque chose ou de quelqu'un». Even then, you can actually omit the article «à droite de la poste», for instance. Other cases is when you take the reference from yourself, such as "at my right", «à ma droite». But when giving directions and turning in the streets, it's always «tourner à droite et ensuite à gauche».
How can you hear difference between elles tournent and elle tourne without any other clue
Unfortunately not. « Se tourner » (the reflexive verb) only means rotating your body (or your head, depending on the context). In that context we turn toward somewhere, and the only choice here is « vers la droite », not « à droite ». So the correct way of saying it would be « Elle se tourne vers la droite ».