How long do u wait for nap time

LT

I’m trying to figure out how long do I struggle with nap time before giving up. There are some days where she has a good 3-4 naps a day. Other times it’s like 1, maybe 2. Today, for example, she was showing signs of tired (yawning, rubbing eyes, been up over 2hrs), but she’s been in her crib for over half an hour without sleeping. She was almost down a few times, then wakes and starts yelling and blowing raspberries. She’s not crying or upset, so I’ve been leaving her and just checking on her. But just wondering when to throw in the towel. She’s 6 months