From what i read on IRS publication 519 and reading the description you have given about your neice above i feel that she does qualify as a resident. Please read the following example posted on irs website :

Lola Bovary is a citizen of Malta. She came to the United States for the first time on March 1, 2007, and resided here until August 25, 2007. On December 12, 2007, Lola came to the United States for vacation and stayed here until December 16, 2007, when she returned to Malta. She is able to establish a closer connection to Malta for the period December 12-16. Lola is not a U.S. resident for tax purposes during 2007 and can establish a closer connection to Malta for the rest of calendar year 2007. Lola is a U.S. resident under the substantial presence test for 2007 because she was present in the United States for 183 days (178 days for the period March 1 to August 25 plus 5 days in December). Lola's residency termination date is August 25, 2007.