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There is no way to sponsor someone for a tourist visa formally. However, you can write a invitation letter, which speaks to her character and confirms that she can be trusted not to overstay. See HERE for an example This would be very helpful to the US consular agent reviewing her application.
Also, needless to say, she has to show ties to her country such as employment (as she has now), real estate contract (ownership/lease), family, etc.
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