Without more details it's difficult to respond to the (mis) information someone else says. Your daughter can bring a vehicle from out of state into California and register it here. She'll also need to pay use tax on the purchase price when she registers it here.
There was a time long ago where some cars were manufactured for CA and then the rest of the US due to CARB regulations, but I haven't seen anything like that on modern vehicles since the 70s or maybe the 80s...tough to say since I've been driving diesels since then and things like cats are handled completely differently.
If the vehicle being sold has been modified and/or non-original engine/parts are installed then she will have difficulty getting it past the referee and smog. That is, if the seller removed all of the emissions equipment and is telling your daughter that it can't be registered in California, that's the reason and it's accurate for all practical purposes for this specific vehicle and not vehicles in general. If it's just some relative/friend opining about the ol' days then take it with a grain of salt.
