how do i take a gmail account off a HTC Droid Eris (Verizon)?

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i got a HTC droid and then when it was to complicated for me to understand... i switched with my niece to had a blackberry curve and she took my droid. but i had my gmail account saved on the droid and i don't know how to get it off because she is getting all my emails plus i am getting the same emails n my BB ..... help me ... please