Hello OP, I hope your forthcoming trip to Granada gives your DD the answers she needs as to whether to pursue a full UG degree in Spain or, opt for a year abroad solution that may be more easier to navigate.
My DD completed a YA last year, 6 months of it at Granada. But her programme was not in social sciences, more a multidisciplinary one that included languages, all taught in Spanish including Arabic, which was a double challenge.
Whilst the requisite for her home University was just pass/fail, many returned to their respective universities with a fail, the marking bar was high, with no leeway for those being non native in class vs their local counterparts.
But she absolutely loved being there. The teaching experience wasn't anywhere as strong as her other semester in another country, but the Granada vibe for international students was great, though I'm not sure she could have done 4 years there - a year for sure. I was expecting it to be more grungy vs other Spanish university cities (sorry to any local PP's above)! but it was really friendly and accessible by foot. And the moorish/European overlap makes the City really interesting, culture wise.
Accommodation was circa £280 per month plus bills in a private house share of 4. There are many private Halls if that's the preference, but more expensive.
The location, whist a pain from UK, is good for them for onward travel if that's of interest to your DD, access to North Africa, ME, rest of Europe etc, well served by LCCs.
To further prepare your DD for total immersion, she could make use of the good value language schools in Spain, mine did a couple of weeks in Barcelona mid A levels, and then au paired in Madrid for 2 months post Y13 (no visa challenges here, you go on an au-pair visa). Yours sounds very language able, so tutoring through studies may also be an option for her, it's funded my DD's UG years of study/extensive travel well and is portable to wherever they are studying.
Sorry this is long post, but I cannot answer whether it is advantageous or disadvantages a UK student, but from a subjective perspective from my DD's school cohort who have graduated last summer or are graduating now, studying overseas has not held them back in their next stages (post grad studies or first grad jobs). I think you need to have an independent, outgoing YP as there is not the level of nurturing as you get here, and the local students do tend to live 'off campus' so do probe these factors on your recce.
Good luck!