OtoHNS_MD is right, sounds like your doc was diagnosis salivary gland stones, which can be pushed out by increasing saliva flow, by sucking on sour stuff like lemon. Drink lots of water! An ENT can consider cutting out the stone, but that's rarely needed...
It's not clear by your post where exactly these stones are located. I assume you're talking about stones within the salivary glands since she was told to take lemon drops. Drinking a lot of water will also help. She should see and Otolaryngologist (ENT surgeon) if it doesn't go away.