"Rehema loves a purple skirt"
Translation:Rehema anapenda sketi ya zambarau
Either sketi or skati should be accepted according to the dictionaries I use.
I have found the DuoLingo Swahili program has a lot of grammatical errors in English. I think the differences in Swahili are because this program is based on Tanzanian Kiswahili. I have heard different pronunciations and vocabulary used in rural SW Kenya.