I claim my mother as a dependent on my return, but in 2022 she sold a parcel and was issued a 1099-s. Does she need to file a return even if there was no capital gain?

Yes, she does need to file a return for Form 1099-S. 

 

This list from the IRS includes the situations that require the filing of the form when received.

Generally, you are required to report a transaction that consists in whole or in part of the sale or exchange for money, indebtedness, property, or services of any present or future ownership interest in any of the following.

• Improved or unimproved land, including air space.
• Inherently permanent structures, including any residential, commercial, or industrial building.
• A condominium unit and its appurtenant fixtures and common elements, including land.
• Stock in a cooperative housing corporation (as defined in section 216).
• Any non-contingent interest in standing timber.

But you may be able to claim your mother if she meets the qualifying requirements to claim a parent.

 

From a TurboTax Help article:

Qualifying relative

• They don't have to be related to you (despite the name)
• They aren't claimed as a dependent by someone else
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident
• They aren’t filing a joint return with their spouse
• They lived with you the entire year (exceptions apply)
• They made less than $4,400 in 2022
• You provided more than half of their financial support

When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them. There may be other tax benefits you can get when you claim a dependent.