First, I am so very sorry for the abrupt and tragic loss of your soulmate. I can't imagine a stronger human sorrow.
No, you are NOT a terrible person for having romantic feelings for another so soon after your soulmate died. And yes, I believe that if your loved one would want you to carry on, then you should do so while making them very proud of you at the same time. Don't think about mourning time limits like one year, three years, 10 years, or forever. Go with what your truest of hearts tells you loud and clear. Arbitrary time limits have no useful purpose here.
I curled up in a ball after my soulmate died and was very vulnerable to each emotion that overcame me. One minute I was feeling so blissful, basking in my soulmate's eternal love, and the next minute, I was plunged into the deepest of despair, feeling utterly lost and alone without him on planet Earth.
Losing one's soulmate makes us feel very vulnerable indeed. It reminds us that none of us are invincible, none of us are meant to easily handle the human experience alone, and there is no cure for the broken heart, except perhaps to give it more genuine, unconditional love and acceptance.
My advice would be to make sure that your romantic feelings for this person aren't there simply because they profess their love for you or make you feel less alone. Your loneliness right now will be at an all-time high, and there is nothing wrong with seeking comfort ... so long as you realize your heightened emotions may be a bit too intense to truly see that person for who they are or what feelings they may have for you.
If your feelings and her feelings are on the same page in an open and trusting environment, then you have a decent chance of sharing your heart and loving fully again. But take it very slowly, and make sure she realizes that you are barely beginning your new journey of living without your soulmate.