Thoughts on where I stand or do?

Context:

Seeing a girl from school days, we always liked each other but never got together. Forward many years (26 years of age now) we have been speaking and hooking up for the last year. She’s met my mum and family members etc etc.

We have respect for each other. She was friends with a boy in school and they maintained contact after school.

He lives in Australia and comes to the U.K. because his family is here. When he comes they go out and have drinks etc etc. This year he did declare his love to her.. I teased her one day about it and made a joke and said “did he declare his love to you yet?“

And she replied with “how do you know he hasn’t already?” Jokingly but with truth.

He messages her and they talk via whats app

Am I getting the wrong idea here thinking maybe this is not worth getting into. We have a lot of respect for one another but I also understand women are women. Does she seem as a potential line up if all fails.. potentially.. should I worry or just see how it goes and keep it red pilled until/If she fucks up?