Malayalam
Malayalam is one of the dravidian language which is the official and native language of Kerala state. As per Articles 344(1) and 351 of the Indian Constitution recognized in its eight schedule Malayalam as a language.
How to learn
Learn Malayalam is one of tasks which may create difficulty to form a sentence because the sentence structure is different from other languages. However it can be easier if you are learning with native speaker. You will get lots of books but it helps to learn what is Malayalam but you will face difficulty to speak. There should be a trainer.
Select a trainer
You can find out the trainer as your wishes but you have to be sincere with learning the task. Find out the native speaker is one of criteria and experience is not a criteria to select a trainer but it is differentiate between the trainers.
Method of teaching
Different teacher has different method it may group class or one on one class. My suggestion is to select one on one class it will be more benefits because the trainer get more attention to students.
Number of students is selecting criteria
Not at all but it only fact that she has teaching experience with more than students if you are selecting native speaker definitely you will learn Malayalam to speak. Eg:- if you have class who is Malayalam native speaker you will learn something from him without a class at least you will learn what he is talking in Malayalam. For my experience I was studied in Aligarh Muslim University so my almost class mates are north Indian students among other Kerala students I used to speak them in Malayalam because I very difficulty to speak English I can read and write English but I never speak before. I studied in Kerala and Malayalam medium school , so no need to speak English that was my problem. That's time my class mates told me I don't know Malayalam slowly they learned what I spoke with them in Malayalam so selecting native speaker is one of the criteria.
Gender is a problem