RES laid two random eggs

Question
I have two RES and they are both girls. Today, one of them laid two eggs.  I don't know which one though.  One egg was laid in the feeding bin, where is got crushed by their weight and the other one in the aquarium.  The one that I suspect laid the eggs was the one that has been really grouchy for the past 2-3 months.  She would try to attack my other turtle.  I a very confused about the whole thing.  Here are my questions:

1) Why had my turtle been trying to attack my other turtle?
2) Is it possible that female RES can lay unfertilized eggs?
3) Is it normal that she laid two or should their be more?

Thank you for your help!

Answer
1. are you sure theyre both girls???????  
Turtles lay eggs even if not fertile.Female can retain sperm for seeral yrs and use it when they want.
They do not have to mate to lay eggs. they cn and do lay non fertile clutches.

The ammt depends on her. If she feels like the situation is ok, she can lay mre. She cna reabsorb the eggs. She can become egg bound and have eggs rupture you have to be careful.
It also depends on the size of the turtle.