First of all Sakura sucks....Lol. In all seriousness we cannot determine who would win because we haven't seen Kushina in battle using any techniques or jutsu.
Kushina, a mother always wins O_O
But serious now, I don't know. It's not like we have seen her in a battle or so. But if she still has the Kyuubi, then she would probably win. I don't think Sakura is a match for a Jinchuuriki
kushina can use her raw chakra to bind the ninetails, she might be able to do the same to sakura. Plus she won't go down easily cause of her resiliency. So most likely Kushina.
academy student kushina could take out a genin. I don't think Sakura ever showed that kind of talent.