How do you make a dog a little less jealous of another dog?

like im dogsitting my bestfriends dog just overnight and they always go on walks together and love eachother but now that mahtoska is actually in my house rosie is very jealous and wants my attention and if im giving her attention and mahtoska comes up she attacks her! and i yell no and scold her but she still does when ever mahtoska gets close to her otherwise its fine if they keep there distance..but how do i make rosie feel like i still love her the most while at the same time making mahtoska feel welcome?? without makin rose jealous.