Translation:My older sister spent too much money recently!
I can see why "My older sister has recently spent too much money." is incorrect. It's COMPLETELY different. If I heard that I realize now that I would be so confused and would have to ask for clarification.
This course did seem to straight to beta, best to just report it and hope the devs are still working on it.
We just learned that hūa means flower and then they give us a sentence using its other meaning...
Native here. Without any information I would assume it is one sister. To avoid ambiguity we can say 我的姐姐都… or 我的几位姐姐. If they are not real sisters, but (senior) buddies, then we can call them 我的姐姐们. You may want to replace 姐姐 (older sisters) with 姐妹 (sisters).