I couldn't be certain about this because I haven't done the research. However, in my opinion I think they are all created names.
She prefix 'She' or sometimes "Che" is quite popular at the moment.
Shemara - is probably just Mara with the She prefix. Shemika - just a different form of Tamika, I think. Shemahlia - again, was probably just Mahlia / Malia with the "she" added. Sherece - I actually this this is probably just an alternative spelling of Cherise.