"Buffy was in heaven but didn't mention seeing her mom."
That's because the "gallery" was actually a front for a smuggling operation. Why do you think she always brought so many things home when they did "inventory"?
And after the whole fiasco with the cursed mask, she brought Giles on as her consultant and fence for the mystical items. This is why he still had plenty of money during season 4 when he had no job and the real reason he bought the magic shop, as a front for offloading those items. It's also why Giles had the statue that melts eyeballs the Council pointed out was a crime to remove from its country of origin; and potentially why Giles conveniently fled the country a fee months after his business partner "died of natural causes".... 🤔