My mom accidentally claimed me as a dependent and her return was accepted. So she will file a 1040x to correct it, but do I need to wait until it is processed to file?

have you checked the rules to make sure your mother can't claim you?  the rule is if you can be claimed you need to check the box on your return whether or not the person entitled to claim you actually did.  assuming mom is not entitled to claim you, she should not have submitted an amended return until her original was fully processed.  this could delay her refund.  since you have been claimed, you'll have to paper file.  e-filing opened officially on 2/12/21. refunds normally take 3 weeks, per the IRS. so she would have gotten any refund around 3/8.  if you mail in your return today expect the refund process to take longer. normally a paper return takes 4 weeks from mailing to process and then more time for the refund to be issued.