Assuming that the first flight is booked under the AS flight number, then this is actually a question for Alaska Airlines, not Cathay.
From:
http://www.cathaypacific.com/cx/en_H...-baggage-rules
So it depends whether AS adopts "first marketing carrier" or "most significant carrier" rules. If they adopt MSC then Cathay's rules apply since it has the trans-pacific leg and then you are correct that the baggage allowance would be 2 * 32kg for the entire journey (or 3 * 32 kg if she has CX Gold or above, or OW Emerald status).