One of the possibilities is that Malti talks to Avni and then she says I found out who she got the money from, that is Malika and Avni says NO ITS NOT HER and I am not telling you who na na na na lol ( I didn't watch few episodes so not sure if malti already knows that she didn't get the money from Malika)
and Mati says this to Vinu and Vinu informs Ranveer.
This is the most easiest approach from what I see cause , vinu going to Malika or Ranveer going to Malika is out of the question
and it is PRETTY obvious this is why the creatives made AVNI the witness to crime.
Cause she has a big mouth and naturally she will be gloating this all to Naveen and Ranvir/and-or Ragini will find out the truth.
VOILA !
Going to Malika dosen't fit the picture .. poor girl. Love is blind and in her case thats a BLATANT PROOF.