At his point you will not be able to MOVE either plant. All you can do is try to train the cucumber to grow away from the tomato. Hopefully it will remain short and tomato will grow tall enough be reached over the cucs. Around our garden the cucumber and squash die off about the time we would need to harvest tomatoes!
Add a little more compost and something for the cuke to climb. Once it starts climbing, it shouldn't bother your tomato and, with the extra food, both should be able to thrive in the same space. Consider how well weeds thrive in the grass of a yard.
Due to limited space, I have that problem with my zucchini and tomatoe plants. I just trim some of the zucchini leafs away from the tomatoe plant so that it can get more sun and grow. Seems to be working ok.