In my opinion, Aarti's fault is bigger. She deliberately hid the truth of her divorce status, while Paridhi didn't deliberately sleep with the producer. She was taken advantage of.
Paridhi lied about going to work, yes, but this is what I call a "majboori"... her family wouldn't allow her to work, which she didn't know before marriage. Aarti on the other hand knew the family didn't want a divorced bahu before marriage, but still got married into the family...
So in my opinion, Aarti's lie is worse.