Yea, I agree... but that is Twinkle's character, she is impulsive and selfless...she cares for her loved ones to the extent that ki she is ready to do anything for them... anything... without been bothered about what will happen to herself... as she said in Mahi's case... she will jump from a building if she says... like wise she is ready to do anything for her father in law also...
and to an extend Kunj is attracted towards her for her this selflessness...
But now yeah, she is not bothered about herself, she is selfless, but there is someone who cannot tolerate any kind of trouble reaching his wife... she is very important to him, so thoda sa bhi pareshani happens to her he cannot tolerate...
So that is their relationship... they are the way they are, they love each other for the way they are... so no one is at fault... they are just living their relationship...