You should have had a serious conversation with your mother before applying for the adjustment of status (green card). You should have explained how long it takes and what it entails. She cannot use green card as a visitor US visa. If she gets LPR status (green card) she should be spending majority of time in the US.
Now, you already rang the bell that cannot be unrung. She demonstrated the immigrant intent and that will make it difficult to obtain another B2 even if this case is withdrawn. I believe DS-160 for B2 visa asks a question whether anybody ever filed an immigrant petition for her. From now on, she will have to put Yes as the answer.
If she travels now, before AOS is completed, she's risking getting her B2 visa revoked AND inability to re-enter US. Depending when her latest I-94 expired, she may have accrued unlawful presence in the US, which can lead to 3 or 10 year bar (ban to enter the US).
Obviously, if she must leave, she can leave, but you would have to visit her back home or in third country instead of her travelling to the US moving forward.