The pop star (and now author) was snapped out and about Saturday afternoon in West Hollywood, where she hit dinner at the Chateau Marmont with her manager, Cade Hudson. She also had a furry friend tagging along ... and even got in the driver's seat as they left.

Like we said ... Brit's radiating here, flashing a huge grin as paps fired away -- and walking along with a lot of confidence, this while rocking a bright orange outfit, boots and shades.

From the looks of it, you could say she might be quite pleased over the fallout of "The Woman in Me," which came out about a month ago now ... with tons of juicy nuggets.

We're not gonna rehash all of it here again, but let's just say ... she gained a lot of extra sympathy and support as people processed her stories and claims -- which is interesting, 'cause you could argue she'd, perhaps, been losing a little steam post-conservatorship.

Now, however ... Brit has the public back in her corner -- and she seems to know that. Of course, there's also the fact she's getting a nice cut of the net sales of the book -- and so far, it's been a hot-ticket item ... with over 1.1 million copies sold in the first week!

So yeah, she's cleaned up nice and then some in the aftermath of all this.

As far as the driving, well -- here's hoping she slows her roll and can stay between the lines on the road. She's already gotten hit with a couple traffic tickets over the past year or so.