Hi Ann!
In my experience here on BW, it seems that 5 months is a tough time for babies. I believe it to be growth spurts, teething, milestones, and a personality explosion (as I like to call it
). Afternoons are what some people refer to as the "social hour" which isn't really social, but actually fussy. I think it's great that you can read her so well to see that it's the fact she doesn't take a full feed that is affecting her sleep.
My advice is to maybe wait until 9:15 for her next feed. She may need a few moments to fully wake up ad realize she's hungry.
When my ds was 5 months and having quite the "social hour" I would make each consequentual A time more and more low key. In the morning it would be errands, after lunch would be outside or tummy time, afternoon was music/me reading to him/a Baby Einstein video/ just anything low key. It really helped us out
Let me know how you get on
- Beca