María Estela Pedroso, who knew the brothers, said she had tried to convince the authorities to relocate her for over a decade.
- María Estela Pedroso, who
- Knew the brothers
- Had tried to convince
- To relocate her for over a decade.
- No error
had been trying will be used instead of had tried past perfect tense is used in the sentence which started in the past and continued for some time in the past. In the sentence, she had been trying to convince the authorities for a decade. So it continued for some time.