Either way, secure messaging requires care from both sides; even if you both use Signal your counterpart can, say, let some spyware screenshot her jailbroken Android, and then it’s all for nothing. The only way of avoiding that is probably handling communication on a dedicated device, or a thoroughly locked down software ecosystem.

Anecdotally, a couple years ago I lost the entirety of my WhatsApp conversations and contacts after changing phone: I missed the opportunity to enter a code at some point and it got wiped without any way to recover it. I don’t know if that was an indication of backup encryption, but it sure felt like security trumping convenience.