I guess she doesn't have favourites based on mother tongue just random liking hoga. Maybe she finds their voice good, or singing 'special' in someway and that might be the reason she likes them . But the fault happens when The creative heads/or judges start favouring the person whom Lata ji mentions is good. That is where it goes wrong. And the creative heads/judges favour those contestants to maybe please Lata Ji, and keep them in the show.
Maybe Lata Ji is just tweeting her opinion and not expecting this favouring, But maybe creative heads interpret it in the wrong way. I dont know :P
But the bottom line is- that shouldn't be the reason of elimination of other deserving contestants.
Eg. Honestly, I feel Shrilakshmi is wayyy more deserving than Niharika. But Niharika is kept in the show because she is Lata Ji's fav. Perhaps. But because of it, Shrilakshmi lost an oppurtunity. And going by Previos history, Lata Ji favourites are made runner ups by the show. So mostly, another contestant who deserves to be in the top 2 will lose his/her spot because of Niharika or maybe Ronita/Ajay( since someone was saying that judges are considering to bring one of them back. They are not Lata Ji favs. But since they are brought back, God knows what is going on the minds of Creatives and Judges.)