$50 is truly a significant amount to be getting wrong on, Olivia Pisarek.
I know how frustrating this is to you, but I have to be honest here. Once a gift card is redeemed, its value is added to the account that redeemed it, and unfortunately the balance cannot be transferred (Refer to Microsoft gift cards terms and conditions | Microsoft Support):
That said, since this happened accidentally, just yesterday, and none of the $50 has been spent, it's worth contacting Microsoft Support. I can't promise they will be able to reverse or transfer the redemption, but reviewing is the appropriate next step for an accidental redemption like this:
- Sign in with your account at Contact Us - Microsoft Support
- Enter / choose an issue > click Get Help to make a request
- Scroll down > click Ask our Support Assistant and follow guidance
- If the issue persists, specifically state in the chat box that you need direct help.
- The Contact Support button should appear > click it > select the chat in browser option
Explain that the $50 gift card was redeemed to the wrong Microsoft account by mistake, tell them when it was redeemed, and make clear that the balance is still completely unused. Have the gift-card receipt or other proof of purchase and the email addresses for both Microsoft accounts available.
Note: The support contact team only works at certain times, so if the last window shows that it's unavailable, try opening it again the next day. If you prefer phone support, you can leave a phone number. This way, they can call you and help you. If you don't see chat option, choose another category and ask to escalate.
I wish I could help more directly, but payment-related issues often involve privacy information. Microsoft Q&A is just a user-to-user support forum, we do not have access to such sensitive account data to verify and resolve the matter.