Especially with only Lightroom you're going to have to get it very right in camera. To do that you need to shoot in daylight or with only neutral soft lights as you can see there is no Yellow lights, there is no Sunset, there is no hard shadows.

That's further emphasized in styling of the decor and outfits. Soft pastel colors, whites, and generally soft to very soft shadows.

She has a few exceptions like this one, https://www.instagram.com/p/BJOXGE9BNAe/?taken-by=laybabylay&hl=en but overall that's all there is really.

Find a room with a lot of natural light, fill it with soft colored objects, and you're there. Only take pictures in those rooms when the soft light is coming in enough to blow out the outside. Colors are almost entirely saturated so other than maybe minor tweaks to white balance there's very little clean up you should need to do. At most a Desaturation of 12-20 may have occurred. Here it is with the color readjusted to their true self, in this particular image it was about an 18% bump to saturation:

The right side of this image is from IG unedited, the left side has a slight bump to saturation.

Beyond this and you get inaccurate colors to key elements. Curious George's signature yellow for example. Skin tones start looking off. And that Cyan poster is already pushing the limits of what even Pantone can offer.

It is certainly possible that on the other hand very, very, very extensive and selective changes were made in post production but I find that very unlikely with such consistency. Most is done by decor and outfits with a very minor desaturation in post.

Alternatively, you could stage the whole thing with a high powered soft box with a neutral / white light directly outside what looks like a window.