Hi Sailorbunny :)
I'd wait a bit, till she's at least 5 month old. So says the Textbook
of Rabbit Medicine (F. Harcourt-Brown), and "Immature females have
thread-like uterine horns and tiny ovaries that can be very difficult
to locate." Besides, sex hormones help develop muscles and bones,
premature spay/neuter might make them weaklings, imho.
For the time being, she can wear a bunderwear! haha... Get an extra
small pantie (or a kid size one), cut the sides, attach a velcro
closure, add a pantie liner, and Thumper is good to go! Oh, and make
sure to take a pic of Thumper wearing the bunderwear, and share with
us ;)
xoxoxo
T. (aka SophiaBunny on yahoo)