I don't see it necessarily as a red flag. There are many good reasons why a woman might not wish to move away from using emf's. If she is insecure about her poor English skills or appearance, she might not want to put at risk what she has at this point of time.
I would persist with asking for a webcam chat. This has to be done respectfully and kindly and gently, but after some effort I would give it away if there is not progress on this.
I am a big believer in triangulation - you need at least two independent sources of information about anything that matters to you.
If you rely on just emf mails, there's a big chance you're going to end up unhappy. There are just too many guys here (myself included) who have relied on emf mails and found that there is a real gap between the woman you imagine from her emf mail and the real life woman.
If you have another secondary source of information about a person (eg your experience with her on webcam, the recommendation of someone you know and trust, time spent with her when you visit her, etc) then the information you receive through the primary source (eg emf mails) is a lot more valuable to you, since you have a way of verifying it.