My oldest dd got a phone at 13 because she was participating in track at school, and the return times varied tremendously. It was an old phone that had very little capability. It was more for our convenience than for hers. We could actually shut the phone down to only send/receive calls from 3 pre-determined numbers. (mine, dad's and g-ma's) Still, I know first- hand the bad things that come from smart phones in young hands.
Younger dd, now 9yo, has begun carrying a phone to gym practice. We carpool a lot, and it makes us both feel more secure knowing we can text or call to "touch base". It's my old phone, and only cost an extra $10/mo on our plan. She also uses it to VERY occasionally call or text her friends from gym on non-gym days. She is very responsible for her age, and MOST IMPORTANTLY, totally not interested in boys at this point. She spends very little time on the phone, and I monitor everything. (no Facebook, Snapchat, etc.). I actually worry less about her use of the phone than I did with my older dd. Also, dh works from home and is frequently on our house phone. Dd and ds use this phone if they need to reach me after school.
I don't think a phone is necessary for young kids, but, they can be convenient when needed and harmless when properly monitored. I would definitely not give in just because "a lot of her friends have one". (And I fall into the camp of believing too much technology is shaping the future of our society in a very negative way.)