"Thank you, Maha."
Translation:شُكْراً يا مَها.
Arabic uses يا as a way to respectfully answer the person you are speaking to. At least that's what I have got from the usage of the word until now. In another example, it can also be used to say يا ماري to mean "Oh Mary". In this sense it also shows endearment towards the person. I hope that helps you understand why it is there.