Catholic baptized in another church A catholic wanted to have her baptism blessed under full water method. The Church is not familiar with this , so she had a evangelical church do it. So, her local Catholic priest forbid her from receiving communion. She was not aware of the consequences of minor excommunication. Now, what can she do to go to Communion again?
We don't have all the information to be sure what is going on, but here are some likely scenarios.

The Catholic Church has no objection to baptism by immersion. It's a completely valid means of baptism, and Catholics do understand it. However pouring and sprinkling are considered equally valid. Moreover most Catholic churches are not equipped for immersion baptism. If your friend specifically requested baptism by immersion then the priest may have declined out of practicality.

Additionally the Catholic church considers baptism a one time thing.  If your friend was previously validly baptized then the priest will have declined to baptize again. Doing so would be a sign that the first baptism was invalid, which would go against fundamental beliefs.

The issue therefore was likely not being baptized by immersion, but deciding to get a major events in their Christian Life done in a church other than the Catholic one. This is not really consistent with a full commitment to the Catholic church, or a belief that it is the best church. Getting baptized in another church will have been taken as a decision to join that church , and by implication leave the Catholic church. The other church will have taken it that way. Joining another church makes you ineligible to take communion in the Catholic church.

If this immersion baptism happened a long time ago and your friend now wants to join the Catholic church, that should not be a problem. She will have to go through formal acceptance into the Catholic church, but that will likely not involve another baptism.

If your friend truly did not understand the implications of what they were doing then they should talk to their priest to sort it out. However that is very unlikely. The other church will likely have insisted on some instruction before baptism, and that will have included implications for membership. They will also have assured themselves that your friend follows Evangelical  beliefs, which would be different from Catholic beliefs. The Catholic priest would certainly have explained the implications if the question had come up.