Yay on STTN! You said the only thing you changed was the food before bed, but isn't the A time post-nap longer too? Weren't you doing more like 4 hours before? And when all was said and done it was 5 hours when she fell asleep. I think with that 3 hour nap she really was able to stay awake closer to 5 hours -- and since she slept thru the night it's pretty clear she wasn't OT!
With a 1 hour nap you're probably going to have to keep A time post-nap closer to normal length -- so more towards 4 than 4.5. But really, I think more A time on long nap days will help a lot.
Teeth can absolutely be at work here too. Those canines are worse than the molars for most babies. They are working under the gums and causing pains (and tiring them out!) even when they aren't showing typical teething signs. Experimenting with pain meds might give you a clue. The canines were like no other teeth we got! Even the 2 year old molars were easy compared to those buggers. They are sooooo pointy I think they must really hurt, even under the gum.
There is a big SA phase at age 1 and another at 18 months. So you could be seeing the beginnings of the 18 month one. It's possible having gma do a sleep period caused some worry in her. We had a similar problem when I had to go out of town for work 3 random days in a 3 week period. To help my son, I started saying at nap time "When you wake up, mommy will come in and say 'hello Owen! Did you have a good sleep?' And then we'll hug and play!" Giving her that speech before nap and bedtime -- letting her know you WILL be there when she wakes up -- may help to alleviate whatever worries she may have with regards to separation. Seems goofy, but it really works.