You said its a 2000 focus, how many miles? Thats pretty important. That things probably almost done if your at or close to 200k miles. The only way a transmission last past that is if its maintained really well, like transmission fluid fill and drains every 35k and full flushes every 70k.
With that in mind, the fact that she hit something is suspicious, look under there and see if you see anything obvious. As far as price, For a 2000 focus wagon the transmission work is gonna be close to value of your vehicle in cost. Sad but true, unless its something super easy. Which at the point its grinding, its probably something internal failing.