I won't accompany with her due to expensive flight fare and previous engagement(선약).

>>>I won't accompany her / I won't go with her due to expensive fare and a previous engagement.

She will have a good time with her family.

>>>I'm sure she will have a good time with her family.

I hope she'll come back without any problem.

>>>Wow!
Do you know the yellow sand phenomenon?

>>>Correct! ( Yes, I heard it from one of my students before.)

We are suffering from the yellow sand every year, especially it gets stronger in Spring.

>>>We suffer from the yellow sand every year especially during Spring because it is stronger in this season.

If the yellow sand rush into the Korean Peninsula from China, the sky turns into gray and cloudy.

>>>If the yellow sand rushes through the Korean Peninsula, the sky turns into gray and cloudy.

The whole world is crowded with tiny dust. The yellow sand has a bad effect on health.

>>>Great!
We can't do little things to prevent it because it is occurred from China.

>>>We can't do even little things to prevent it because it comes from China.