A friend was trying to send me bitcoin using a Bitcoin ATM, she sent the funds to "her phone number" instead of my wallet QR code. The ATM indicated that Bitcoin was sent, but my friend doesn't even have a wallet address. It seems like a wallet address was generated for her and we don't know how to retrieve this bitcoin back, can you help?
it seems like a wallet address was generated for her
This seems most likely to me. An ATM should not allow the destination/receiving address to be empty or to contain something that is not a valid bitcoin-address (e.g. a phone number would be rejected)
A phone number might be requested for an online custodial wallet service with two-factor authentication (2FA) - if so you'd need to find out the URL of the service, and the corresponding username and password or other credentials.
If your friend doesn't have a printed receipt with some details on it, it is likely that the money is now forever inaccessible.
- try to find a printed receipt
- contact the ATM owner (although I would not expect them to be able to help)
- visit the ATM with your friend and try to recreate what happened with the minimum possible amount of money as a test.