I learned that you had to put a comma before and if a 2nd subject was introduced, but if the subject was the same, it was optional. So it would be

She did, and he did

but it could be

She did, and she did
or
She did and she did.

If that makes sense.

But commas are not my friend. Perhaps they were filling my head with lies smile

Grant me the serenity to accept the things I cannot change,
The courage to change the things I can,
And the wisdom to know the difference.