User A owns a book. User B borrows book from A, which is now shown within "Books I'm Lending" for User A (and Borrowing for User B). User C searches for the book and clicks "request to borrow". The modal displays the option to borrow from User A and User C requests. User A confirms checkout of the book by User C.
User A still sees only User B within "Books I'm Lending". User C still sees the option to withdraw the request.
User A owns a book. User B borrows book from A, which is now shown within "Books I'm Lending" for User A (and Borrowing for User B). User C searches for the book and clicks "request to borrow". The modal displays the option to borrow from User A and User C requests. User A confirms checkout of the book by User C.
User A still sees only User B within "Books I'm Lending". User C still sees the option to withdraw the request.