“about a bow shot.” About 100 yards (100 meters), more or less. Far enough to be near her son, but not see him from where she was.
“lifted up her voice and wept.” An idiomatic way of saying she cried loudly and uncontrollably. She had lost her home, the father of her child, and now was on the verge of watching her son die and likely herself as well. Hagar began to cry uncontrollably.