What to use She didn't have to or she didn't has to?
And please explain little bit !!

Question

Answer

You never say "didn't has". It's simply wrong.

When you use "didn't", the main verb doesn't change: "She didn't have to."  In fact, for past tense verbs, there's no difference between I/you/we/they and he/she/it.

Answer

Prashant:

This is one of the biggest mistakes made by learners.  If you remember one easy rule, you will NEVER make this mistake again:

After DO / DOES / DID you ALWAYS (no exceptions) use the BASE form of the verb (the infinitive with NO "to"):

She DOES not HAVE to eat.

He DID not HAVE to write.

DID she HAVE to study?

DOES he HAVE to drive?

Answer

Use "she didn't have to."  It's the correct form of the conjugation of "to have".

I have
You have
He/she has