Player wants to be Elsa in Rime of the Frost Maiden

One of my players has chosen to be a draconic sorcerer electing to prioritize cold magic for this campaign. I warned that resistances and immunity might become an issue later in the story if they stuck with that. She's not much of a power gamer and often times neglects such mechanics, so I gave the elemental adept (cold) feature to help with resistant enemies. This however has turned out to be not very useful as more and more enemies are immune.

They just hit level 5 and she's going to be getting more spells now so that might help, but if it doesn't does anyone have any good ideas for how to handle it? Should I just let this player deal regular damage in spite of the cold resistance and immunity?

Any thoughts are welcome.