Yes she isn't any where close to moving on right now, I agree , what with her shuffling with Dev's pic as her pastime at night in her phone , but that doesn't mean she isn't trying n she won't try .
And that doesn't mean her relationship with R is doomed from the very beginning. Actually far from that . Rithik and she are spending lots of quality time with each other on a daily basis , going out regularly , she has even started to smile and chat when with him , even Elena couldn't make her do it but R can.
R is not n nor he gonna push her into being a wife in the real meaning of the term soon post-marriage. Till now his character is immensely positive n supportive n understanding . So why not get married first and move on after marriage ?? Is there any rule you must sort out your feelings for your ex before the marriage happens ?? If the groom has no problem waiting for as long as she needs , then who are we to object ??
By the way , it's absolutely Sona's right whether she'll get engaged and married to Rithik while still in love with Dev . No body can question or dictate her on this. It's her marriage her life and she isn't hurting any body or being dishonest with her future partner.