Your questions answered
Doctor Woolfson's Answer:
It might be that she is afraid because the toys are so large. Her rocking horse will be physically much larger than her, and perhaps she finds that intimidating. One solution, therefore, is to think about the toys that seem to frighten her, and then identify a common theme that links them.
If it is their size, then there are two strategies you can adopt. First, try to find smaller examples of the same item, such as a smaller rocking horse or a smaller stuffed toy dog. A second solution is to gradually get your 15-month-old used to the toys that upset her, perhaps by having them in the same room with her as but keeping them well away from her. Then, over a few days, play for a while minutes with your daughter in the room but each time play closer to the object that disturbs her, calming her if she appears to be upset. Eventually you and she will end up playing beside the large toy, at which point you can suggest she gently touches it once then leaves it alone; in each successive day, steadily build up her contact with the item in this way, until she is no longer afraid.
Another possibility, of course is that she has learned that reacting badly to a toy is a effective way of getting your attention. If that might be a factor with our toddler, stay calm when she gets upset, smile as you reassure her for a few moments, and then get on with what you were doing before she started making a fuss.