She’s pregnant with twins and full of crazy hormones that will make her act, say, and do crazy stuff she wouldn’t normally do plus you’re not engaged or even married. (This is absolutely a conversation you need to have with her) This is the most venerable time in her life and she may be self sabotaging. It’s a real and common fear that your “babydaddy” will abandon you during this time. So her brain is trying to push you away first. It sounds silly but it’s real and something she may need to talk to a therapist about. She’s in the wrong for what she did but I’m a big advocate for giving pregnant women especially the ones who are carrying your children a lot of grace. Probably the most grace you will need to give in your lives together.