Hi, and welcome to The Tortoise Table (sorry, I don't know your name). And many congratulations on getting your new Horsfields -- they are a great species with lots of personality). And I love the names Flo and Wilma -- I have two Horsfields called Doris and Dolly.
If you only got them yesterday it's entirely possible that Wilma is just settling in, as some tortoises take much longer to feel at home and confident, so I would give it a little while and see what happens.
You've set up a really nice looking tortoise table (and thank goodness you weren't sold a vivarium, as there are great problems with those). The only things I would suggest are:
1. That isn't an ideal substrate that you have, as it is not as good for them to burrow into and it is also a fire hazard. We know of at least one case where a lamp blew and the hot pieces of glass that fell onto that substrate (it was hemp/aspen/aubiose) started a fire. I used to use that when I first got my tortoises, as it was all the rage then, but there were reports of some sharp ends of the hemp scratching a tortoise's eye, or causing internal problems if it was digested.
The best substrate to use is one that most closely approximates their natural substrate in the wild, which is a sandy soil. So we now recommend a mixture of ordinary sterilised topsoil and children's play sand, and you can buy bags of these at places like Homebase or garden centres. You mix it either 50/50, or perhaps a slightly higher percentage of topsoil to play sand. And then you give it a light spray every day or two so that it is the tiniest bit damp and that will keep it from getting dusty. And make it nice and deep so that they can completely bury themselves if they want to.
2. The only other thing I can see is that you won't be getting an adequate temperature from that thermometer mounted on the wall, and it's possible that it is much hotter under the lamp than you think (which could be why Wilma is moving to a corner). You need to measure the temperature directly under the lamp, at the height of the tortoise's shell, so you might have to take that thermometer off the wall and hold it there for several minutes. The best type is one of those digital fridge/freezer thermometers that have a digital display unit and then a probe on the end of a long cord that you can hang down so that it is as close to the circle of light as possible. Something like this (but you can get them in lots of places and it's good to have one with a max/min function so that you can see how hot or cold it got since you last looked).
https://www.amazon.co.uk/Digital-Freeze ... B071WKGTJL
Sorry for the long message, but basically you've got a really good set-up there, and a couple of tweaks will make it perfect.
Best,
Nina