Why does one pronounce बहन with an "e" there, even though it is not displayed graphically?
The ह sound causes this phenomenon in most of the words that it occurs in.
Example -यह , वह, छह, बहन, शहर, कहना etc.
There were a few posts in this forum explaining this phenomenon. You should scroll down and read them. Or you can just keep track of ह words because most other words are very phonetic.
Why would this not be either of the other answers (son or brother)?
Oh, just reading a little more about this, the confusion clears. The मेरी (my) used here is female because the object is female?
it can be like : This is my brother or daughter also right , how can it restrict to sister alone?