Is she literally ignoring you - eg; not responding to you? Or is it more of an issue of her being busy?
If its the former, then she's very rude. If it's the latter, then it's pretty normal. I have good friends who disappear for a bit when they are very busy.
I have to add: she's not interested romantically. If she was, she wouldn't be too busy to be in contact
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.