I don't think we ever learned what she called her mother to her face, but when talking about her, Tara used 'mother' like in the following scene from The Body:
TARA: My mother died when I was seventeen. BUFFY: I didn't know. I'm sorry.
Willow: How long have you been practicing? Tara: Always, I mean, since I um, was little... my, my mom used to, She um, she had a lot of power, like you.
From what others have already said about canon and from where we pontificated (way back when) Tara was from, 'mom' is how Tara would address her mother.
I had a discussion about this with some LJ friends and we thought she might be from one of the more rural and obscure bits of California - if only because they couldn't imagine how she could afford out-of-state university fees, given her dad's attitude.
We figured (very) Northern California to Southern Eastern Oregon to Central Oregon. Areas like Klamath Falls or LaPine or any of a dozen super tiny towns with no industry or growth since logging.
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on 2006-01-06 11:42 pm (UTC)TARA: My mother died when I was seventeen.
BUFFY: I didn't know. I'm sorry.
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on 2006-01-06 11:44 pm (UTC)no subject
on 2006-01-07 12:02 am (UTC)Willow: How long have you been practicing?
Tara: Always, I mean, since I um, was little... my, my mom used to,
She um, she had a lot of power, like you.
I think "Momma" sounds in character.
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on 2006-01-07 12:06 am (UTC)no subject
on 2006-01-07 12:08 am (UTC)no subject
on 2006-01-07 06:42 am (UTC)no subject
on 2006-01-07 09:32 am (UTC)no subject
on 2006-01-07 11:02 pm (UTC)no subject
on 2006-01-07 10:57 pm (UTC)