German Shepherd dog

I have an 13 month old female who has not come into heat yet (unless it was a silent heat).

I did not have any males to warn me about it until 1 month ago that I got my first male.

Having asked the vet he said that he has seen females coming into heat even when 22 months old. Is this normal?

Is there a way to find out if her reproductive system is OK?

Thank you all in advance.

One of my WGR show line females didn't come into a full blown heat until almost 13 1/2 mos old. But I've heard of other show females coming in around 6 1/2mos old.  So it pretty much depends from individual to individual.
If a female is very meticulous and clean, they can keep themselves pretty clean so that you might just miss it, especially if there's not a male around to let you know. If you keep a female around other females in close proximity, they usually will trigger each other to come in heat.
You should be able to take a look at her privates and tell if she's been in heat yet. Females who haven't been in heat have very small private areas-still puppified. Once they go thru heat, they usually swell and then stay larger.
Other than that, watching close and waiting is the only thing I know you can do.