This girl think I'm hot and a nice guy: how do I ask her out?

I really like her and she told me I'm a hottie and a few times she says I'm a nice guy. She knows I like her and Iv asked her out a few times. Everytime I do she says aww but she either has to go to work or she already made plans with someone. I know I should move on but she has been really close for three years and I was her very first friend since she moved here. When we first were getting to know each other we were kinda flirty and she looked at me in a way like she wanted to say something and would look away. Sometimes she smiles and sometimes she doesn't. She was always the girl I could talk to when I was dating other girls she would give me advice and when other girls were sexually flirting with me she would say ewww or she would leave the room. We have been seeing each other slot for two months and hanging out around our busy schedule. Its hard to visit her sometimes because I usually visit her in the morning when she would just wake up and she would still me half asleep so I would kiss her on the cheek and tell her go back to bed. We both love each other and I want to be with her but how do I do that?