When this happened leaving my EE all alone she was also duly terrified. I got 2 ready to start laying, one looked just like the Barred Rock friend she had lost. The other was a hefty size red ranger.
The newbies came from the same flock and were known to each other and it was required to buy a minimum of 2. RR took on lookout duty straight away. BR being younger than the one the hawk killed not only was more docile than the deceased (which had just started laying and pecking the EE in a bid for dominance) but looked similar enough that EE was happily relieved - fooled and got off to a great start having dominance restored to her sans competition. The RR is relatively a dumb eating machine at this point, but too big for hawk and unafraid to leave coop first for treats.