Do you think its right?

so i have a friend who ive known for a very long time and he had a grilfriend that i became friends with...ever since ive seen her i liked her...so recently my friend joined the army and left to japan and wont be back for a long time so he broke up with his girlfriend and before he left he told me it was ok if i went out with her..so shes still getting over him and we hang out sometimes but only as friends cause im scared what she might say if i tell her that i like her...do you think its ok that i ask her out or should i just stay friends with her??