I'm less concerned about whether the shoes will get ruined and more about whether unsuitable shoes will leave the kid's feet cut up and blistered to the point where she can't walk well. That happened to me more than once at that age--not because I insisted on unsuitable shoes but because we didn't have a good handle on what worked for my feet then--and it may not have had the long-term health consequences a sunburn might, but it made even getting back to the bus to go back to school difficult.