Betty's Gemstone is located at the bottom of river at Bamboo Grove. To find it, simply jump down from the top of the waterfall and proceed dive down from the corner of the rocky left bank of the river. You have to pass the red bridge in order to get to this area.
Betty's Gemstone is a quest-related item you need to find to claim the quest's rewards in Slayers 2. Since this process can be tricky, especially for newer players, we created this detailed guide on exactly how to find Betty's Gemstone, so stay tuned!
Where is Betty in Slayers 2?

To begin searching for Betty's Gemstone, you will need to speak with Betty and start her quest. She is located at Bamboo Grove, atop a cliff overlooking a large waterfall, which is roughly 600 units to the left when leaving Windy Peak (the initial spawn location).
If these instructions seem vague, there is another way to find her. Walk to where Bamboo Grove is spelled out on the minimap, and stand just above the letter "R" in "Grove"; Betty will be there. However, you can only start her quest once you reach level 10, so make sure you do that beforehand to avoid wasting time.
Where is Betty's Gemstone in Slayers 2?

To find Betty's Gemstone in Slayers 2, jump down from the top of the waterfall where you initially talked to Betty and walk alongside the left bank of the river. Pass the red bridge and head to the corner of the rocky shore on the left. Once you are there, dive into the river, and you should be able to spot it immediately.
This item is dark blue and shaped like two pyramids glued together at their bases. Once you approach it, you will need to collect it by pressing T, since it doesn't pick up automatically. Once you do, Betty's quest will automatically complete, and its rewards will be added to your balance, so you don't have to speak to her again. These rewards include about 700 XP and 240 Wen, and they will instantly propel you to level 13 if you complete this quest as soon as it becomes available, which is when you hit level 10.
If you want to travel faster, make sure to also check out All Horse Mount Spawn Locations in Slayers 2 – Horse Taming Guide.