Non verbal/ verbal explanation?

So your first question is no she would be considered verbal bc she can say words. Non verbal autistic children tend to only make sounds if they make sounds at all. And your second question the answer is yes, she could follow directions. She could even follow complex directions if she’s autistic. Autism falls on a spectrum. Some needing a lot more help than others and needing a lot less help than others. More typical signs would be is she making eye contact? Answering to her name? Wanting to be social with other kids or is she wanting to play alone. But you can still do any of those behaviors and not be autistic.

Hello! BT here, I work with kiddos with autism so hopefully I can help? At 21 months the main things you might notice with autism is her ability to respond to her name or to share attention (if you point at something and ask her to look, she should look). Another thing is babble - she might not be using full sentences, but might say "eat snack" when she wants a snack. Every kiddo is different, though. You're absolutely doing the right thing by having her repeat phrases and reinforcing by giving those items to her. It could be the delay she's experiencing is related to glue ear; similar speech delays are seen in kids before they get glasses, and they typically learn very quickly once they have glasses. It's still good to keep track of the things you noted in your post, but her current speech progression wouldn't necessarily be labeled as non-verbal behavior.

My son is 3 and autistic he’s non verbal and can’t follow instructions

Autism is a spectrum and the three pillars of difference to look at would be:
• Sensory differences
• Emotional and social communication differences
• Rigid/ inflexible in behaviours

If it is purely speech you’re concerned about, I would strongly suggest adding in other forms of communication - we use Makaton and it is brilliant in enhancing communication where spoken words can’t always be used