Teddy considered that for a moment. If she was his mother, she must be from a point before he was born (which, admittedly, was 99% of her life). He wondered if he should give this her (alien or mother) any information. He had to tread carefully here.
"Nymphadora. That's my mother's name," he said. He purposely left off her surname, and tried to avoid past tense. "What's your mother's name? Just to make sure you aren't tricking me." If she was an alien she wouldn't know Grandmother's name, Teddy was sure. Mostly sure, anyway.