Sisterly empathy?

Earlier today Ella got a spanking for jumping on the bed. She cried and cried! I pulled her onto my lap to cuddle with her while she was crying and to talk to her about why she was punished. The entire time Ella was crying, Brenna was going BERSERK! She kicked me repeatedly until Ella stopped crying. As soon as Ella quieted down, so did Brenna. Sisterly empathy or coincidence? I'm not really sure, but it was a weird experience.