CONGRATULATIONS! What an amazing opportunity for your granddaughter!
How is the family going to make a living while she's working? Or, is SHE their living? It makes a difference in how to advise her.
There will be far less money than anyone would think. First, she won't work every month. So, it's $32k/mo, but only for 8mo/yr = $256k. And then...
35% taxes
15% to Coogan Account (required by law)
10% to her agent
10% manager?
10% biz expenses
5% lawyer?
Leaves her about $40k/yr. She should max her SAG-AFTRA 401k and invest in a total market fund. (Now she's down to $20k/yr!) The Coogan Account is essentially her college fund. She can't contribute to a ROTH. She'll make too much.
The life of any series is between 1-8 years. She may or may not have a career when it's over, and should plan for the worst-case scenario. She must educate herself, take an interest in, and be thoroughly involved with her finances, just as though she were an adult. Her parents should assist, and indeed INSIST, that she be informed, and have a voice in the decisions. Nothing should be done without her knowledge.
Now, she might have additional work outside or related to the series... but this is the advice I'd give to start.