What is the difference between "з" and "із" ? Is the latter used for pronunciation purposes only?
More correct English would be "with her sister," unless the context is so specific that both people in the conversation know who she is, they know she has multiple sisters, so "she is there with 'a sister' [meaning one of them]"
Isn't there a way to say this using "туди"?
Shouldn't «Вона є там з сестрою» be accepted? If not, why?