If she is a permanent resident of the USA (has a green card), she should reside permanently in USA. She cannot be absent for longer than 1 year without a re-entry permit.

If she loses her status for whatever reason, yes, when you are a US citizen, you'd be able to petition for her again.

If you’d like to schedule a telephone legal consultation, please let me know, and I’d be glad to help and advise you: Attorney [@] law-visa-usa.com

Note: The above response is provided for legal information purposes only and should not be considered as legal advice. This response doesn’t create an attorney-client relationship, which can only be established through payment of a fee. If a follow-up advice on your specific situation and regarding U.S.A. immigration-related issues is requested, we can offer a paid consultation by telephone or email to clients from all States and globally. Please visit our website http://www.law-visa-usa.com/contact_us.html for more details. Our contact email address is Attorney [@] law-visa-USA.com

Generally, when a Legal Permanent Resident remains out of the country for more than one year without a reentry permit, it is considered as abandonment of the green card. If your mother loses her green card, you can petition for her if you are a US Citizen.

Please note that this is very general information and should not be considered as legal advice. If you have more (specific) questions, please do not hesitate to contact our office for a consultation. You can visit our website http://www.parwanilawfirm.com for further details.