Which uses the correct modifiers for formal writing? Mom said she thought Maria had been treated wrong and that she should stick up for herself. Mom said she thought Maria had been treated wrongly and that she should stick up for herself.

In formal writing and communication, the sentence "Mom said she thought Maria had been treated wrongly and that she should stick up for herself." is more appropriate. Although wrong and wrongly are both adverbs, some writers consider using adverbial "wrong" as incorrect, so you might want to play it safe and use "wrongly" instead.