Just for the record, Arina Martinova is just 4 months younger than Kimmie Meissner. For the purposes of ISU eligibility, they are the same age. While Arina doesn’t have quite as much experience as Kimmie, it’s because Kimmie had better National and International results than Arina did and so she was sent to competitions at a younger age than Arina..
2002-2003 Season
Kimmie won the 2003 US Novice Championship and was sent to the Triglav Trophy, where she won the bronze medal in the Novice division.
2003-2004 Season
Kimmie went to the 2003-2004 JGP, where she won one silver and one gold medal, and finished 5th at the JGPF. She won the US Junior Championship in 2004 and went to Jr. Worlds 2004, where she won the silver medal.
Arina was on the substitute list for the 2003-2004 JGP, but she was never sent. Arina went to Russian Senior Nationals in 2004 and placed 9th. She was not sent to Jr. Worlds 2004.
2004-2005 Season
Kimmie went to the 2004-2005 JGP, where she won two silver medals and won bronze at the JGPF (behind Asada and Kim). She won the bronze medal at the 2005 US Senior Championships, but was too young to go to Senior Worlds. She was 4th at Junior Worlds 2005.
Arina skated in the 2004-2005 JGP, and finished 4th and 6th in her two events. She was 8th at 2005 Russian Senior Nationals but was not sent to Junior Worlds 2005.
2005-2006 Season
Kimmie went to the GP and finished 5th in both of her events. She won the silver medal at the US Championships and went to the Torino Olympics, where she was 6th, and to her first Senior Worlds in 2006, where she won the gold medal.
Arina went to the JGP and again finished 4th and 6th in her two events. She placed 6th at Russian Senior Nationals and was sent to Junior Worlds 2006, where she was 12th, and to Senior Worlds 2006, where she was 19th.
2006-2007 Season
Kimmie went to the GP and won a silver and a bronze medal.
Arina went to the GP and placed 7th in both events.
So--both ladies have been to 4 JGP events, but Kimmie went to 2 JGPFs; Kimmie has been to 2 Junior Worlds, Arina has been to 1; both ladies have been to one Senior Worlds.
So the experience that Kimmie has over Arina is a Triglav Trophy, two JGPFs (because she won JGP medals and Arina didn't), one Junior Worlds (because Kimmie finished higher at Nationals), two GP events (because Kimmie went to the JGPF twice) and the Olympics (because Kimmie medaled at Nationals and Arina didn't).
ETA: I am sure Arina is a very nice girl. I have nothing against her personally, but I do not think that her skating is special in any way. Cup of Russia was one of the lighter events in terms of competition, and Arina finished 7th there.