Translation:She is very flexible because she is a secretary.
It's not a mistake; it'sa perfectly valid notion. Did you ever entertain the idea of flexibility being an ability to adopt, adapt, and improve in a workplace scenario and that this exercise simply presupposes a secretary's ability to do so, irrespective of his or her physical dexterity or acrobaticism? Again, your mind went there.
Yes, my mind went there. That's why I commented.
There is a broad pattern of questionably sexist and explicitly aggressive content in some of the learning material. For example, questionably sexist: so far secretaries in Duolingo sentences have only been women. Explicitly aggressive: the sentence "she's a little ugly, but not bad." I could point out many more examples.
If I had to reach far to make the point I wouldn't make it, but since the case is right there I've shared what I've seen. We have the most constructive community here when everyone participates.