That is a bit big. The only big problem with that is your T might not be able to find the food you offer. I keep smaller Ts in small kritter keepers or other containers of similar size. But she will grow into it thats for sure. If you stay with that container just make sure you drop the food near by her so she has a chance to kill it right away.
Oh and she will burrow to, slings love to dig, so shes more then likely going to dig and you wont see her much. But there is no way to stop that really, once she is bigger the digging stops usually. My adult females are out all the time now. But my juvies and slings are pet holes.
Well you just graduate her as she grows. Once she seems cramped in the container your going to put her in transfer her to a bigger one, and so on and so forth till she makes it to the home that is meant to hold her as an adult. When she is at about 3-4 inches you can put her in the home she is meant to be in forever. Thats what I do at least.
I have 4 B. vagans slings. I kept them in fill cannisters until they became 2cm. From there I graduated them to a small aquariom I designed, 3x3 square by 4" deep. I fill it up with substrate 2 1/2 inches deep. The lid is made out of 1/4 inch plexiglass which slides shut on top through an aluminum frame. I drill 3-6 holes on the plexiglass so it'll have some kind of air movement inside but still keep humidity as needed. When they burrow they usually pick one corner of the encl;osure so I can still see them. When they molt, I wait until the new skin has regained their natural color then I dig them out again so I can get the exuvium and clean the enclosure of detritus that may have accumulated throught the month. I got my slings february this year and they were 1.5cm then. All four now are 4cm LS and very healthy. will post a pic of my enclosure later so those with the knack for DIY's can do it. Each enclosure would cost a little under 2$ equivalent in my currency.