Have to Blend Forehead Botox Treatment with Glabella Treatment?

You can certainly treat the forehead lines by themselves and not treat the frown lines. You may still want to put a small dose of Botox into your frown lines as a preventative treatment to prevent needing higher doses there in the future. More and more, we are using Botox not just as a treatment, but as a prevention so that lines/wrinkles don't "etch in" which is much harder to treat.

Your forehead can be treated on its own, but make sure you see an experienced injector so you do not develop lowering of your eyebrows.  When your frown lines are ready again for treatment, your forehead should be reassessed as well.