Not sure whether these stats help in predicting or not, but...
Her outdoor PB is 51.61 from 2024 in Savona, where she ran Sharlene Mawdsley close (51.43). That is also the year she set her 800m PB (1:54.61) That 400m was her opening race of the season in mid May. She went on to have two more races at 400m at the 400m at the UK Champs, and made the final where she came 7th (heat and final outside 52 seconds).
In 2022 - when she was 1.5 seconds slower over 800m than her 2024 PB - she ran 52.42 indoors and then 52.41 outdoors at the UK final and came 5th. So her indoor & outdoor times were basically identical.
In 2023 - when she was 0.5 seconds slower over 800m than her 2024 PB - she ran 51.76 outdoors (no 400m indoors) & came 3rd at the Euro U23, some way behind John & Jaeger. She had run one 400m prior in the season, a 52.24, one week after her then PB over 800m of 1:55.77.
So she has been chipping away at that 400m PB over the last 4 years, and whilst her 51.49 indoors this winter is a big improvement from her 54.42 in 2022, that was the last time she ran it indoors, and her outdoor PBs have all been small(er) reductions.
Thinking it over again, I don't think she will break 51 in Rome. Even though her indoor 800m shows she is in better form than 2024, I think chipping off nearly half a second off that indoor PB is the max she will do. I am going to predict a 51.1