Selecting fabric for a quilt is so hard. I always fear that I won't end up liking the finished quilt, even when I can actually see the fabric in person. That is why I ask the person I am making the quilt for to select the pattern and the fabric. That way they get what they asked for, and everyone is happy. It is too late for that...sort of.
You could do what suern3 suggested, and keep the quilt. Then you could share with your sister a few simple patterns that you are comfortable making...even as a beginner, there are some you can enjoy making. Have your sister select the fabric, and then make the quilt yourself. You could tell Sharon that seeing the quilt she made inspired you to make one for your sister yourself. If you are unsure of sandwiching the three pieces, perhaps Sharon could do that part for you...for pay, of course.
I really feel for you. Making a quilt is not cheap, and now you have a quilt you don't really like. Have you seen it in person? Maybe it will look better to you in person. Sometimes the border sort of makes the quilt.
At any rate, welcome to the board. I am sure you will get more advice. Folks here have good ideas.
Dina