It is probably more likely to be a one off, than a new trend. If she goes 8hours at 13 weeks you are doing fantasticly well. So enjoy those times she does do it & don't deny food on the times she wakes up.
But as you know she is capable of it, give her a chance to resettle if she just whinges. She may also go through a growth spurt & need more, so trust your instinct.
My philosophy is if my ds#2 (4.5mo) wakes at night he gets fed if it is more than 4 hours since he last fed. I bf & I never deny food, he mostly goes 8-10 hours but on the odd night he doesn't I feed, as I feed if he wakes he needs it.
If the wakeups become exactly the same time, then it may not be hunger & that is the time to look at other re-settling.