My former guardian (22) and I (16, boy) are in love. My friends say: this is forbidden. Is that true? She now works in a different establishment.

What your friends say is only partly true.
It is never forbidden to be in love.
However, it is different where physical contact is concerned.
A guardian may not have sex with your or kiss you.
You are their ‘ward’ and you are dependent on them.
The person protecting you may not have sex with you.
Even if you want to.
It is forbidden.

It is different when she is no longer your guardian.
Then it is not legally forbidden.
What’s important is:
You must both want a relationship.
You must both want bodily contact.
If you both really want the same thing then it’s OK.
However, sometimes it’s difficult to know if you want to.
Sometimes you want to make somebody happy.
Then you do things you don’t really want to.
It can be hard to tell the difference.
Maybe you can talk to somebody about it and get some advice.