Here's the thing though: Yamato only wants to join Luffy because Oden joined Roger. She believes what Ace told her about Luffy becoming the Pirate King, and so she sees Luffy as the next Roger.
Don't believe me? EVERY time Yamato has brought up wanting to join Luffy, she always finds a way to bring Oden into it
When she meets Luffy and announces she'll join, she says that "as Kozuki Oden" then Luffy is obligated to have her join. When fighting Kaido, she repeatedly states that she is Oden as she says she's going to sail with Luffy. When meeting the crew, she introduces herself as Kozuki Oden.
Yamato's desire to join the crew is inherently linked to her desire to be Oden. And no, she doesn't simply idolize Oden; she wants to be him.
Joining Luffy would not be following her own path. She'd simply be following the footsteps of Oden. And quite frankly I don't think that's going to happen, especially given what's happening with Aramaki. Yamato choosing to stay in Wano would show her deviating from the path of Oden, and forming her own path.