I'm new to the net but not Aikido, 32 years experience training and teaching, so I hope this observation is taken in the spitit it is given.
Learning Aikido is really hard and takes a lot of time and help from many people along the way. Often those ukes which we find to be problamatic from both sides of the too hard/too soft coin turn out over the years to have helped us learn some of the hardest lessons.
I understand that young woman very well. See if you can distill your attempts to 'do' aikido to her by simply trying to locate her center when you are paired. At least it will be something and you might come to look forward to training with her. Every single person on the mat can teach you something. Every one. You really have to look outside the box, sometimes, but it will be there.
As for too soft ukes, I think it is a great way to train for feeling intent. Often an attacker will hide his intent or not even be aware of it building in him. If we learn to seek out subtle intentions and movement we become more able to deal with these things. It keeps us from being surprised. It also turns lemons to lemonade on the mat.