401/403

I was hoping if you could answer a question for me. My mom had to leave her job for health reasons. She borrowed $1000 from her 403B account a few months ago. Now that she doesn't work there, she received a letter stating that the $5000 in her account is no longer hers because she missed a scheduled payment that is taken out of her check. She still owes $750 and has always paid on time. Is there anything that we could do that would allow her to keep her money?Thank you so much