Since you did not mention where your sister is going, can't tell if the International warranty of these brands will cover that country
Asus - most models come with 2 years international warranty (but certain cheap models only have 1 year warranty).
Dell - extend warranty to 3 years (~ RM300), then the warranty become international warranty.
Lenovo - most models come with 2 years international warranty (but certain cheap models only have 1 year warranty).
Asus
K46CM-WX060V, B987 + Nvidia GT630M@RM1799[2kg], 2GB, 500GB, W8, OD
A45DR-VX044, A8-4500M + HD7470G@RM1499, 3GB, 500GB, FreeDOS, 2 year warranty
Dell
Inspiron 14-3421, i3-3217U + Intel HD4000@RM1399[1.99kg], Win8SL, 2GB, 500GB(5400rpm), 4-cell
Inspiron 14R, i3-4010U + Intel HD4400@RM1549 [2.32kg], 4GB, 500GB(5400rpm), W8 , 4 cell
Lenovo
G480, Pentium 2020 + Intel HD@RM1399, 2GB, 500GB, W8
G480, i3-2348M + Intel HD3000@RM1299, 2GB, 500GB (5400rpm), FreeDOS; W8@RM1499
G480, i5-3230M + Intel HD4000@RM1499, 2GB, 500GB (5400rpm), FreeDOS
Prices are RSP, negotiable.
Dell
Inspiron 14-3421, i3-3217U + Intel HD4000@RM1399[1.99kg], Win8SL, 2GB, 500GB(5400rpm), 4-cell
Lenovo
G480, i5-3230M + Intel HD4000@RM1499, 2GB, 500GB (5400rpm), FreeDOS
G480, i5-3230M + Nvidia GT635M@RM1699, 4GB, 500GB(5400rpm), FreeDOShope you can top up and pay a little more for a better performance G480, then get an 'ahem' version of windows.

prices are RRP and negotiable.
Well I showed my sister all of the choices you guys recommended. And she said she likes the G480. Though she asked me if there are any other colour beside black. She said she want a blue one haha