You have reason, Aru is Madhav's wife's she's just feeling it now as she was only taken by the swap marriage things and Madhav being Ehsaas whom she expected to be someone very dashing is not but now she has began to recognise his humble personality.Aru always had respect for Madhav/Ehsaas, and I don't think she holds those weird "spots" against him,except for the reason that she uses his spots as a reason to cover up the hurt that she feels that she was not married to Rahul. But keeping that reason apart,she respects and likes Madhav. After all that he has done for her (all those paper leaking issues and dhola-maaru bonding ) it was only a matter of time that she would have fallen in love with him. That love is the reason behind the desire to find a suitable,loving partner for him,after she leaves. It never occurred to her that she would want to stay back as his wife,it was just working subconsciously in her mind.
Now that she sees another woman near her doting hubby,her real feelings are coming out.I don't think it's just because she is losing importance.It's love all that way,that is making her jealous.Hope I am making sense. 😊