The "turtleneck" thing that was totally messed up is that her mother uses "tokkuri." Tokkuri is the word for those tall and thin sake bottles with the especially skinny necks and flared mouths, but it can also refer to turtlenecks (maybe something only older people would say?). Sumika tells her to use "turtleneck" instead, using the Japanese pronunciation of the English word.
The "ma" thing is that in the bubble immediately before, the older sister happens to use the sound "ma" a lot. Then, in their mother's panel, what she says contains "mama" twice as a joke to follow up. The "muhahaha" in the translation especially came out of nowhere.