If her 7th birthday comes on 2 April 2010 or later, then she must be free from fares on subways around Tokyo until 31 March 2010;
in that case, ask JR-East about JR fares and charges on her.
(Its guidance in Japanese explains the same rule as is adopted by the subways,
while its guidance in English says children of 6 through 11 are not free.)

Around Tokyo, there are 13 subway lines of two operators.
Tokyo Metro subway: 9 lines, operated by Tokyo Metro.
Toei subway: 4 lines, operated Tokyo's Bureau of Transportation.

Tokyo Metro subway
- Tokyo Metro: Detailed Guidance: Age Categories for Passenger Fares
http://www.tokyometro.jp/global/en/ticket/age.html
- Tokyo Metro: Using the Subway
http://www.tokyometro.jp/global/en/service/using.html

Toei Subway
- Toei Subway Information: Operations
http://www.kotsu.metro.tokyo.jp/english/subway_op.html
- Toei Subway Information: Buying Your Ticket
http://www.kotsu.metro.tokyo.jp/english/subway_buy.html

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Regards,

Then she will be free until March 2010 from charges at least of the two subways around Tokyo, regarded as a pre-school child. (If she were residing in Japan, she would enter a Japanese elementary school in April 2010.)

JR companies show us two sets of age criteria (school pupils or not, age 6 - 11 or not), which can be confusing. I hope they dissolve it soon.