Well, I just check with the naked eye personally, this one you have here is still fine for this size. Maybe not in the next 2/3 molts. Putting a T in a big enclosure isn't a problem as long as she can hide somewhere and web around.
If she's around 3cm legspan, i'd put her inside a 10cmx10cm enclosure, with a bit of hightness to allow you to add few branchs and not risk to destroy her webs everytime you open the enclosure.
That's what I've done for mine, but she's doing fine tho
Still being a new keeper myself, I’ve learned that enclosures are more often too big than too small.
That said, that enclosure should be fine through its next molt...maybe the next two. I’d take @Otteresting’s advice and have a slightly larger enclosure prepped - maybe as soon as the next molt. Just in case. Sometimes GBBs really explode in size between molts and it’s probably better to have one ready ahead of time instead of scrambling.