Reattribute capital gains reported under one SSN to another individual

I prepared to lend my mother money in anticipation of her buying a house. The money had been in an individual brokerage account in my name under my SSN; I transferred it to a new individual brokerage account in her name under her SSN. But I had full management authority of that account.

While the money was in her account I continued to actively manage it, accumulating significant short-term gains. Before the end of the year she decided not to buy a house and we transferred the money back into my brokerage account.

The broker must report capital gains (Form 1099-B) accumulated while the money was in my mother’s account under my mother’s SSN. How can the 1099s be reattributed to me when we file our individual tax returns?

Because of our relative tax situations this year it will be much more efficient if the gains can be attributed to me for tax purposes. (In fact, I imagine that an auditor examining the situation would argue that the titling of the funds under my mother’s name should be disregarded for tax purposes because: no loan was actually made, I retained control over the funds, the transfer was reversed, and no real benefit accrued to my mother.)