I found both, but my mf sorc is cold.
Is it worth re-specing her into either fire or lightning?

Is that charm so helpful?

Probably not. Those charms are very cheap now, so try trading to a cold one first and try it out. It opens up some areas that are normally cold immune. They definitely change the game for a cold sorc.

Only respect if you, let's say, want to farm pits exclusively with a light sorc and don't have infinity to break immunities. Sunder would break light immune are hers, so you could damage them now, but without -elr, they still have 95lite red (I think)

So only respec for fire/lite if there is an area you want to farm but currently cannot due to immunes.

This is my first MF sorc, completely from scratch; I am poor as hell now lol. I thought I was going to MF a lot of different spots.

Thanks for the advice

Just keep playing. You will find a cold one within 10 hours. they drop like candy.