Eira is pronounced differently in different areas of wales. In many areas of the south - eye-ra while in the north mostly ay(like hay)-ra
Im in the north so I use and prefer the ay-ra pronunciation. It’s a very different name to Miriam. I quite like Miriam Eira like a pp suggested. Where I am Eira is very popular but I’ve never met a child Miriam so due to that, I’d go for Miriam. I am in Wales though so I appreciate Eira might not be so popular outside of wales.