<think>Okay, so Betty needs a wallet that costs $100. Let me start by figuring out how much money she currently has. The problem says she has half of the money she needs. Since the wallet is $100, half of that would be $50. Wait, is that right? Let me confirm: 100 divided by 2 is 50. Yep, so she has $50 saved up already.

Now, her parents are giving her $15 for the wallet. That's straightforward. So if I add that to her savings, it would be $50 plus $15. Let me calculate that: 50 + 15 = 65. Hmm, $65. But then her grandparents are giving twice as much as her parents. Wait, the parents gave $15, so twice that would be $30. Let me check: 15 * 2 = 30. Right, so grandparents are giving $30.

So now I can add that $30 to her total. Let's see: $65 (from her savings plus parents) + $30 = $95. Wait, 65 +30 is actually 95? Let me add that again. 60 +30 is 90, plus 5 is 95. Yeah, correct. So with all that, Betty has $95 in total from her own savings, her parents, and her grandparents.

But the wallet costs $100. So how much more does she need? If she has $95 now, then subtract that from $100. Let me do that subtraction: 100 - 95 = 5. So she needs $5 more. 

Hold on, let me verify each step again to make sure I didn't make a mistake. Half of $100 is $50. Parents gave $15, grandparents gave double that, which is $30. Adding those up: 50 +15 =65; 65 +30=95. Total she has is $95. Wallet costs $100, so $100 - $95 is $5. Yeah, that seems right. I think that's the answer.
</think>

Betty currently has half of the $100 needed, which is:  
$$\frac{100}{2} = 50 \text{ dollars}$$  

Her parents contribute $15, and her grandparents give twice that amount:  
$$15 \times 2 = 30 \text{ dollars}$$  

Combining all the amounts she has:  
$$50 \text{ (saved)} + 15 \text{ (parents)} + 30 \text{ (grandparents)} = 95 \text{ dollars}$$  

To find out how much more she needs:  
$$100 - 95 = 5 \text{ dollars}$$  

**Answer:** Betty needs $\boxed{5}$ more dollars.