And is it just dialect or does it have a meaning in standard Italian? If so, is it the same meaning or does it have another meaning? Thank you.
This phrase is used to express esteem, admiration and respect to a person. Literally it means that no one can even think to leave that person's company. The verb mollare in this case has the meaning of "to leave someone". In Italian the correct preposition is ti, instead of te, that is dialetto romano. So in Italian you could say "e chi ti molla?".
Other similar forms are "e chi te molla più!" o "chi te molla a te!".
I agree with the comment above. I just want to provide a different context for the sentence. For example, you could say it also for a situation, not only for a person:
"Ho trovato un lavoro vicino a casa, che mi piace e in cui guadagno tantissimo. E chi lo molla più?" --> here it means: I will try all my best to stay and work there. I am not intentioned to leave this work, because I like it very much.
Or, for a person:
"La mia ragazza è intelligente e anche stupenda. E chi la molla?" --> I like very much my girlfriend and I don't want us to be parted.
As you can see, "Mollare" means "lasciare", "leave".
I just wanted to add the origin of the expression. It doesn't come from
molla as a noun (which means spring, coil), but from
molle as an adjective (which means soft, squishy or soaked). From this is derived the immediate and true correct meaning of the verb
mollare, which is a synonym to
allentare and means slacken, loose. From this, and the idea of loosening a rope or slackening a knot, comes the figurative expression of letting something go, lose the grasp or something, or desist.
Also note that the verb
mollare is much more used than the strictly correct
lasciare in current speaking, but you should never use it in any formal context, as it is a rather colloquial and almost slangy term.