Greetings,
If she has the R50 and kit lens, there are only a few choices in the $400-$800 category.
Canon
RF-S 55-210
Single lens solution Canon
RF-S 18-150
Single lens solution Sigma
Contemporary 16-300mm for Canon RF
As Marc indicated, it's very difficult for us to make meaningful recommendations without a budget and knowing what gear she currently owns now.
Some people don't mind carrying and changing lenses. Others want to mount one lens and carry that. While there is no one "do it all lens", people usually make these types of decisions based on the type of photography they do, their budget, and what they're willing to carry.
All three of these lenses have image stabilization. The two Canon lenses will be the sharpest of the bunch. The RF-S 55-210 picks up where the 18-45 kit lens leaves off. The 18-150 is more a single lens solution with a modest amount of reach . These two lenses are more compact than the Sigma, and one would require that she carry her kit lens if owned.
The Sigma would potentially eliminate her needing to carry a shorter zoom. It has considerable more reach at 300mm, however, in its case, because of its longer focal length (and price point) it's corner to center sharpness at max zoom isn't quite as good as the Canon counterparts. This is due to design not because it's a bad lens. It's marginal and only a extremely discerning eye would probably notice. It's the most expensive of the three offering the greatest flexibility. It's also the longest and heaviest. The Canon options or shorter, lighter at the expense of less reach.
Maybe this will help kick things off for you.
~Rick
Bay Area - CA
~R5 C (1.1.2.1), ~R50v (1.1.1) ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, ~RF 200-800 +RF 1.4x TC, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve Studio ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8 ~CarePaks Are Worth It
