From what I remember from Latin courses years ago (please correct me if I make a mistake):
Illa is more like "that woman", 'woman' being implied by illa being feminine singular. But can be translated simply as "she".
Haec (added this for contrast) is more "this woman" but can also be used like "she".
Ea is more a general 'she', can be used for 'this' or 'that' woman.
There are multiple ways to express he, she, and it in Latin. I'll explain just with she.
Illa - that, that woman, she
Haec - this, this woman, she
Ea - this/that, this/that woman, she
Illa is far the more unnatural here I feel. Is, Ea, Id is the literal He, She, It. Using Ille, Illa, Illud is more for emphasis. THAT woman, her, she is the one we're talking about: as opposed to She is doing it. I don't think we should base new word instruction on one of the 3rd of 4th uses of a pronoun. I know Ille, Illa, Illud can sometimes be He she or it as a Latin teacher, but I don't tell my students that at first. Got to build from the basics.
Ea is common as she. Illa is common as she. The course uses both so students will become comfortable with both.
Then why do I not get to use both in the answers? Also, I checked the OLD, made a post with both definitions to be sure. Is, Ea, Id, is used as He, she, it first. Ille -a -ud is used as That first. I'm not seeing That introduced as it's first meaning in the course. So I'm getting the wrong impression. If I didn't know the language I'd run around thinking Is, Ea, Id, and Ille -a -ud are interchangeable, and while they are in SOME situations, they definitely are Not in others.
The course is in beta. That's why both aren't accepted yet.
The words are almost interchangeable. Each can be used as a pronoun and a demonstrative.
Also a Latin teacher
Illa can be a little derogatory, like "that woman". Ea does not have that connotation
No, your confusing illa with ista.
Ille, illa, illud - that / that famous (person/thing)
Iste, ista, istud - that (pejorative)
Generally the finite verb comes at the end of the sentence,especially with a subject and predicate nominative sentence