She can definitely use this to apply for cards on her own. Every FI will have different rules for how they view AU accounts. I have heard a lot of people having luck with Discover (they seem to like thin files). Apple Card is nice because you don't take a hard pull before determining if they will approve you or not. I've also heard about intermittent success with Citi. My daughter gets Citi pre-approval letters all the time thanks to being AU on my and my wife's cards (even though she's a minor).
When I turned 18 (back in October 2007), I applied for and (after manual review) received a Discover IT card, Chase Freedom card (back when there was one and the categories were whatever you happened to spend the most in), and a Citi Driver's edge. A year later, I got my first AmEx. I had a long AU history thanks to my Dad.
When it is offered, they should check the pre-qualification page.
1/8/17 Discover $18300 CL- $1k SL- AU, wife
1/26/20 AmEx Cash Magnet $35k CL, wife
2/19/20 BB&T/Truist Rewards $11k SL- impulse application
2/22/20 Citi Double Cash WEMC $2.9k-->$4.4k-->$8.4k-->$13.4k-->$17.4k-->$19.4k-->$22.4k-->27.4k AU, wife
3/8/20 Wells Fargo Propel AmEx/Autograph VISA $2900-->$3200-->$5000-->$8800-->$13k-->$15.5k CL- AU, wife
3/9/20 Truist Rewards $11k SL --> $13.5k- AU, wife- impulse app
3/21/20 REDcard MasterCard (TD Bank) $2500-->$6000-->$6500 CL
11/24/20 AmEx Cash Magnet $10k SL-->36hr-->$20k-->$35k CL
6/10/21 SoFi World Elite MC $7000 SL
1/19/22 AppleCard/GS $6k-->$10k-->$11k-->$12k AU, wife
8/15/22 Chase freedom flex $10.3k SL-->$12.5k-->$15k-->$19k AU, wife
7/5/23 Lowes/Synchrony $4k-->$10k-->same day-->$35k CL
8/2/23 Chase freedom flex $19k --> $22.8k-->24.3k CL
8/2/23 Discover $8k SL
