Mom As MOH

I would like a few opinions on this....I am getting married in June. I have a slight problem with my wedding party. We are having a small party (I only have 4 girls) but I don`t have a maid of honor. I have two cousins in my party, and a friend from high school and one from college. My problem is that I have known everyone (but my cousins of course and I can`t choose between them) for the same amount of time, and am not closer to one or the other between my friends. However, I am very close to my mom and thought about asking her, without taking away from her day as mother of the bride as well. Anyone have any suggestions on this? I`ve seen groom`s have their dad as best man, but haven`t seen it this way. Thanks!