I don’t do hijaab but still don’t shake hands with men. But my dad allowed me to shake hannds if a guys offers because otherwise it would be rude. So yes, it would be rude if you do not shake hands with someone who offers the same to you.
But if you do not feel comfortable, you can politely convey your preference to the person. You can politely respond by waving hands and saying ‘I am sorry, I prefer it this way’. May be its kinda rude but you will be able to avoid shaking hands.