I have found that my normally passive horses can become nippy if they are uncomfortable or irratated, and pregnancy is definitly a condition that can bring that on. Just give her some space, excercise her normally, feed her normally, with no extra “because your pregnant” treats, and watch her sugar intake. She doesn’t need any changes in diet or routine now. Don’t put yourself in a proxmity where she can get her teeth on you, but close enough to be a comfort to her. I have to agree with the imprinting comment above, handling is good, but imprinting goes alittle too far in my experience. Kind of like “join up” can backfire too.