Hey Nick and Melissa, Nick is really close here --- but there's a little bit of caveat. With triggers, as long as one of the triggers is met, then the flow steps will occur. Basically, triggers are OR statements, and this cannot be changed.
I would think it would be best to say trigger: filled out form, filter: interest field = xyz. This way, you're selecting people who filled out the form, and have an interest field of xyz.
Hope this helps!