Descendant of the Sun Recap Episode 6
In the ending of Episode 5 our Captain Yoo is returning back to Korea but before this happens he asked Doctor Kang if he should confess or if he should apologize for the kiss. The decision that Doctor Kang made was the apology for the kiss.
Even though there is desire to be together and attraction to Doctor Kang he is charming but dangerous and she doesn't like dangerous things. Her words that he charms her and attracts her, but it isn't enough because every time he leaves and there are funerals.
I cannot blame her, who wants to see their lover and love die from dangers of their jobs. At the same time I don't think she trust him because he lies to her and doesn't tell her what to expect. In addition, when she is trying to decide and make up her mind on him he leaves and since she knows he is leaving because of duty to the country she is unable to voice out her thoughts on it.