[teentodiefows]

2012 Grand Slam Rulebook: http://beta.itftennis.com/media/107012/107012.pdf

Section Z.4.c:
Vacancies
A team shall constitute a doubles entry. Therefore, if either of the
players of a team cannot play, that doubles entry is subject to default
and substitution. However, if a player has to withdraw through injury
or other unavoidable circumstances after the sign-in deadline, but
before the draw, his partner may enter again with another player who
has not already been accepted into the doubles event, and this new
team may be accepted provided it qualifies by virtue of the computer
ranking used for selection. With this exception, players may not
change partners after the doubles entry deadline. In no case shall any
player change partners after the draw has been made unless the draw is
remade due to the withdrawal of seeded team In short: the draw's set, so she can't pick another partner.