If she lied to me, then she'll just have to face the music.
How this sentence is correct?
I think it's supposed to be like " If she lied to me, then she would just have to face the music."
Please explain me this structure.
There are two possible ways to understand if she lied to me.
The sentence seems to mean "If it turns out that what she has told me is not true, she will have to face the consequences." She has given the speaker some information which may or may not be true.
Your interpretation is "If she were to lie to me (at some point in the future) she would have to face the consequences." Would is correct in this instance.