Michael, I think the correct way to answer here is based on how "fast" the seller needs to close. Does "fast" = 45 days? 30 days? 3 days? If they can close in 30 days then a normal mortgage can work. If your mother is planning to occupy the property there are 3.5% down programs and perhaps she can qualify for some "Downpayment Assistance Programs"?
Now, if the seller needs to sell the property in 3-10 days then there aren't many options for that. Some people might think that Hard Money (which can close very fast) could work but if she is planning to occupy the property then Hard Money can't be used.
There is a lot to consider here so feel free to either reach out to me for specifics or just post again here with any other questions. Thanks!