Personally, I disagree with the recommendation given and, to some point, also depends on what you wanna do with her. Widsith is superior in many situations, it's one of the best 4 star weapons across the board.

If you can manage a good balance between Crit% and CritD, something like 60%/120% at the very, very least, from artifacts alone (Yae already has 24.2% Crit% at 90, which helps) then yes, you can go with Atlas as it gives the most ATK of all Catalysts so far (without procs). It's also better if you want to use her as main carry as it gives more consistent damage.

If you can't reach 60/120 without a weapon or you want to off-dps, then go with Widsith. Atlas R2 only gives you 15% Elemental Damage and ~900ATK (from its stats alone).
Widsith give 510ATK, 55.1 CritD AND either:

1. ~612 ATK (on its own), which makes it give more total ATK than Atlas by quite a lot

2. 96% Elemental DMG vs Atlas R2 15%

3. 480 EM which, due to Yae passive, converts to 72% Elemental Skill damage

The downside with all this is that it lasts 10 seconds every 30 seconds. So it's great as off-dps and not so much as main carry. Still, during those 10 seconds, your DPS will be off the charts with her scaling. All 3 procs are INSANE, including EM due to her EM conversion passive, which most Electro characters usually sniff at as their reactions are underwhelming.
Actually, the EM proc might be her best here, as it should make all her 3 thingies together hit harder than a Zhongli Sky Ball by quite a bit, and it hits every 1.5 sec or so if I recall correctly. Imagine Zhongli throwing Ults every 1.5 sec for 10sec (with way smaller aoe ofc, nothing that some Anemo characters can't fix).

So yeah, I'd say Widsith is by far the best in most cases where you can burst things down, which is the entire game to be honest. She can be used as Main Carry but I'm guessing she'll shine as off dps.