I say go NC, and although I get why you would want to text and wish a happy birthday I would say stay silent. where we go wrong is when we think the opposite of love is hate. the opposite of love is indifference. Go no contact and spend time with yourself, family and friends. Spend at least a month away. STOP sending gifts altogether. Gain some perspective. I know it’s hard but it will be better once you see things from the outside. Good luck! keep us posted!
PS: if you do decide to text her on her birthday, keep it short, go straight to the point and DO NOT try to force the conversation further. She obviously wants her space.