Doesn't sound like you've got a choice. Get a 4 gal or larger pot, if the soil has the right water balance so it holds itself together but isn't glued to the sides, you may be able to flip her upside down, give the bottom a thunk and the whole rootball will come out intact. Have the new pot ready with some (good) soil already in it's bottom for correct soil level. Just fill in around the sides, water and relax.
Peace,

Tex