She has always been very good at sleeping and has previously had a good napping routine 9-10am and 12:30-2pm.
However, she has recently learnt how to rock on her hands and knees and will fight sleep until the point of hysteria whenever I put her down for a nap. I often have to just get her up in the end as I haven't got the time or inclination to hang around at home for hours at a time while she whinges in her cot. She also doesn't sleep in her buggy any more (v annoying!), just spends the whole time trying to sit herself up and craning her neck to see the world go by.
I'm not sure what I can do really, other than letting her exhaust herself, because she will always go to sleep eventually, even if it's 6 hours and 3 failed nap times later! It's just really hard seeing her so tired and grumpy all day. And I really need to get out and about otherwise I start to lose my mind!
I really struggled with daytime naps with my LO and felt trapped at home some days because DD needed to sleep and wouldn't sleep in her pram. I brought a snooze shade for the pram and it really was the best thing I have ever brought as just like your LO my DD was just too nosy to nod off when we were out and about. Now when I see DD is getting sleepy, I pop the shade down and she is asleep in seconds, it also works at home if we don't go out