How do Catholics who become protestant come back?

I have a Catholic church who married a protestant in the church, and then formally joined the protestant church. She was baptized, first communion, confirmed in the Catholic Church. If she wants to rejoin the Catholic church, does she have to do R.C.I.A.? Or is she still considered Catholic although she made a profession of faith to a different denomination because once a Catholic always a Catholic?

What if a baptized, communioned, and confirmed Catholic leaves the church and becomes a Muslim? Is the answer the same?

She simply needs to make a good confession and she can resume full participation in the Church.

The only wrinkle would be if she had written a letter requesting formal defection from the Catholic Church. She would then need to write a letter rescinding her previous one.

In either case, she does not need RCIA.

It does not matter if she was a practicing Protestant or Muslim, she is still considered to be validly baptized and confirmed.

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