I agree, it sounds like ellas. It seems Duo uses them as interchangeable on occasion. Wouldn't a native speaker understand if I used ellos or ellas? Might they (native speakers) think my vision is not so good? And these days it can be challenging to distinguish genders of one, much less a group!
I meant no disrespect, I was hoping to allow you the opportunity to learn the word for right (mismo) by yourself, but I see from other people who commented that you know already. Good language journey to you! :-) You should repeat everything you learn at least three times, and write it down if you have to, to remember. May your journey be filled with adventures of peace and harmony.