Is my dog’s behavior considered reactive?

I have a 2 1/2 year old Shih Tzu. At the dog park, she gets along with other dogs. She ignores some and plays with others. She doesn’t bark at them.

When I take her on walks and there’s another dog approaching, she starts crying and then barks viciously. If it turns out that she gets the opportunity to greet the dog (before she starts acting out) then she is fine and doesn’t cry and bark at it.

She also acts like this when she’s in the car and sees dogs outside. When watching tv, she barks at dogs and horses on the tv.

I’m wondering if this is considered reactive behavior. I give her treats and praise on the rare occasion that she doesn’t act like that.

If anyone has any ideas on how to deal with this, I’d appreciate any thoughts or advice. Thank you