What would you do?

My best guy friend has gotten in a relationship. I absolutely adore his girlfriend. After everything he’s been through with other women, she’s been so great to him. She came to me and asked me if I could basically get out of the picture. She wasn’t rude or anything, she was genuinely being nice. I figured..who am I to say no or be difficult or disrespectful about it. So of course! You got it. But recently he’s been texting, calling, ect and asking why I haven’t been to the social events with the crew or answering him back. ( we have never done or been anything more than just friends) I’m unsure how to respond. I don’t wanna throw her under the bus. Him and I usually did everything together, but I don’t ever wanna make his girlfriend feel uncomfortable so I did what she asked. What would you do?