Making relationship official?

I've been dating a girl for almost 3 months.

All is going well, great sex, great chemistry and we see each other about 2-3 times a week.
We're exclusively dating but not girlfriend/boyfriend. Is there a standard time I should be looking at to approach that topic with her?

It seems like what we're doing is already like a relationship with the exception of not meeting friends/family and going on holiday together yet
Making relationship official?
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