User blog comment:FairyRaven/Fairy Tail Chapter 421: Wendy and Chelia, Review and Commentary/@comment-203.215.121.237-20150223133248

Wendy maybe have longer stay in Lamia Scale guild than in Fairy Tail:

After Oracion Seis arc, joined FT, after a few days went to Edolas for a few days too, then Tenroujima for a few days also. Then got frozen in time so time didn't pass. When they returned, after a few days, time-skip again in the Celestial Spirit World for about 3 months then spent a week in Crocus. Tartarus arc must be at least a few days also. Wendy's total time in FT guild must be only a few months while staying in Lamia Scale for almost a year. Maybe that's why her bond with Sherria is much stronger and she's also her age.