Got oral from my brothers girlfriend

my brother and his girlfriend live together throughtout that time we would all hang out and smoke with eachother. his girlfriend is my type and i felt there was signs she was into me. some time pass by and they started having problems so she would text me for advise . and I did. we then started texting more and more frequently and from time to time we would chill while my brother was gone and would smoke. when they split up we still kept in touch and she would ask me to smoke with her and I would deny... one night I was feeling very horny and she texted me to smoke I aggreed.she took me to a abandond road and we smoked there and chilled for a while. eventually the conversation became sexual and i started telling her that i was horny and really horny when I smoked. She smirk and said she could tell I was already hard . I got so turned on with the looks she gave me and I whipped out my hard cock and she got on her knees and gave me head. was probably the best head I ever received in a very long time. Once I came I felt guilt and we went home and didnt speak to her...well she told my brother that I did something and he confronted me asking what I had done . I couldnt tell him and she denied and said she was lying and only doing it to get him mad when he called he to confront her infront of me. He doesnt know she gave me head and I really feel very ashamed of what happend. What can I do??? Should I just confront him him before she spills the bean ?