I actually love her character.
It's obvious she knows that nothing will happen between her and Ranveer, but she is his best friend, and they are comfortable with each other, so that's probably why they flirt without thinking it's something deeper. Remember, it's not just Mallika who flirts with Ranveer but Ranveer flirts with her too, but does that mean he wants to be with her or he plans to be with her in the future? No, so likewise, although Mallika might want to be with Ranveer it seems like she has accepted it will never happen and they are just good friends.
Plus they have been friends for several years now, so she probably knows that if it was meant to happen, it would've happened already.
I haven't ever thought Mallika was jealous of RanYa.. In fact I thought Aaliya was jealous of Mallika and Ranveer, which is a good thing as it will make her realise her feelings for Ranveer.đł