I rode a carbon Domane w 105 and liked but didn’t love it. One issue was not enough clearance to port over my left-only 4iiii power meter.
As a quite old guy I settled on Felt Broam (aluminum) for several reasons: slightly more relaxed position, oodles of clearance for wider tires (both comfort issues), and the new GRX groupset, a nice step up from the 105 in my opinion. It’s not just the improved climbing, but the ergonomics of the new shifters, which might be even more important (so I hear) for women with smaller hands, or for someone changing from hybrid to road levers.
I too came from an entry-level hybrid with flat bars some years back. Drop bars in my mind were for racers in their 20s. It was only after complaining about my hands/arms getting tired / numbing out and buying different extensions and grips that somebody mentioned I might actually be comfier on drop bars because they offered so many different positions – duh. And of course I was, and still am, even more ancient. It’s a couple hundred more than the Domane AL 105, but I think groupset might be worth it, and you can resell it as a real gravel bike.
One consideration about sharing your trainer. I had left my old Shimano 11-32 cassette on my Direto (not Kickr) when I got the new bike (with newer 11-34 cassette). Assumed it wouldn’t matter since I’d be mostly in ERG and wouldn’t have to use the lowest cog anyway. I found that with the indexing adjusted for outside, the bike would occasionally jump cogs on the trainer. I thought it was a problem with the Direto thru-axle adapter, but it entirely disappeared when I put the newer 11-34 cassette on the trainer as well. Not sure if these issues will affect your setup(s).
Good luck. And I guess even better advice than any of this is: share freely whatever info you use to make such decisions, and then get the hell out of the way and let her choose a bike for herself.