As far as I know Armaan Kohli is 48 years old, making him 13 years older than her. That's too far of a gap for my personal preference. But other than that as long as they are two consenting adults who cares if the gap is 13 or 30. Their life, their choices, power to them.
What does bother me though is that the relationship makes no sense. Armaan isn't really an attractive person (but hey different strokes for different folks). It isn't that he is very rich or influential (Tanisha has relatives who are way more significant). He's not the charming great date material (who knows) and he seems more of the get drunk and be a loud belligerent slob kind (the opposite of sexy). So while I don't find anything wrong in the relationship (if it exists), but wonder what Tanisha sees in him.
I come to two possiblities. Either Tanisha is one terrible woman and cannot find a better man or Armaan is exceptionally well endowed beyond belief.