"She walks around."

exactly. she walks around (the city, the world, thr bldg, the child.)

Indeed, this is wrong on Duolingo's part. "Ella camina alrededor" means "She walks around __"; without filling in that blank the thought is incomplete. To get an accurate translation you'd have to change the sentence structure quite a bit with something like "Ella va caminando por ahí". The issue with "andar" is that it doesn't necessarily imply "walking" as much as general moving or going. Also, "Ella anda" is likewise an incomplete thought as it doesn't give enough information about what's going on.

Duolingo is giving a transliteration, you are correctly translating the idea

It is strangely difficult for me to pronounce

That's what I wrote

Were you thinking of "cerca" with an "e" not an "i"?

I think cerca is more for walking around something, meaning walking near to it, which is a little different from just walking around. And in this context I think it's actually "cerca de". Eg: ella camina cerca de la casa.

i don't know. What does circa even mean again?

Circa means around or near. It is used in the scientific literature to express that, although the certainty necessary to provide a unique value is lacking, other reliable data exist that allow to assure that the fact or data that is communicated in the text occurred at a moment -or had a Value-anterior or posterior to that cited in the reference scale used, but always relatively close to the one that is transcribed.

I hate this sentence, it makes no sense to me. Alrededores are surroundings

It's basically an incomplete thought. That's not something you would say in Spanish. You might say "Ella da una vuelta" or other regional variations.

Dar vuelatas- plural- is to go in circles. "Dar una vuelta" -singular- is to take a stroll or to "walk around"

In Spanish, adverbs are typically placed after the verb they describe.

Try saying [Al ray day door]. I think that would be close enough for some one to understand you :)