I think doulingo has drawn their line that they want Elle aime "things" to be like and Elle aime "person" to be love, and the opposite for Elle aime bien. In the real world I THINK this is a little more flexible, but this is where duo has drawn their line.
It's not just Duo, that's how the verbs work. Aimer a person is love. Aimer a thing is like.
Wordreference seems to argue that aimer something can mean like or love but aimer a person is love unless you say aimer beaucoup (or bien).
Linguee says you can translate it as loving or liking someone or something.
Cambridge dictionary follows Duolingos construction.
So all I'm saying is in real life someone will use aimer and depending on the situation it might be like or love, and it may not only depend on if they're talking about an object or a person. Duolingo has set up they're rules to be consistent and accept the most common usage and that's probably good for learners. I still think it's important to remember that language is not math and even if aimer has a very clear and distinct definition in French, "like" and "love" may still be flexible enough in English to meet that definition. Language is almost never as simple as "that's how it works".
For the most part I think Duolingo does really well helping to understand the complicated nature of language. Use words how you want, but now you know how Duolingo is going to grade you :).
I also wrote that. Since it does not have bien after, Elle aime bien cela, it should read as she loves that. I don't understand the reason it is incorrect, either.
"this" and "that" often are interchangeable in English... not so in French?
Wouldn't "Elles aiment cela" also be correct, since the pronunciation is the same?
Since aiment starts with a vowel you should hear the liason between Elles and aiment. So there would be that z sound in the plural version.
I've got a longer post in this thread explaining in more detail, but cela is going to refer to an object normally and not a person. Doulingo holds the rule that "aimer" something is to like it and "aimer" someone is to love them. Like I said in that other post, I feel like there's more wiggle room in the real world but at least Duolingo is consistent.