Actually i dont know about mandvis charecter at the time of swayamvar
But as far as i heard from ny teachers in school...
Mandvi is a nice women but the difference is she somewhat like power authority..but never had problem with sita...and ram..but after marriage to bharat..there will be a point of time to decide the legal heir and become raja..for this as per the rules there will be competetion bwn two bros...so someine should compete with ram..but all 3bros refuse to participate and request dasaradh to declare ram as future king..then mandvi asks him to compete as he is also worthy...but he refuses her..later ram takes promise from bharat to participate with scincerety...later ram wins it through his kind nature...then mandvi asks him why he broke the promise given to ram as she thinks he lost knowingly...then he says he gave promise to participate but not to win so i did not break any promise...
Later when bharat decided to move to lake side hut until ram returns from vanvas..she supported him and asked him to take her along with him but he refused and said her to take of urmila and other 2 mothers in their absence...
So as far as i heard..she is indeed a nice person..
In yest epi also she was uncomfortable when ravan is insulting sita..and afraid when she saw his original roop..
Sorry for long post and make u bore...just thought to share these with u all
Thank u