Swine flu symtoms??????????

how long until symptoms show if you get swine flu? My sister has just returned home to australia this morning from overseas after living in uk for a year, she went to new york 2 weeks ago. I am dying to see her, but i have an 8 week old bubs and a 15month old who is currently sick with gastro so his immunity is down already. If my sister is carrying the bug how long til her symptoms show? I don't want to risk my kids getting sick but really want to see her!!! She says she feels 100% well at the moment