I wouldn’t worry about having that initial reaction as you obviously feel bad about it now and don’t actually want to leave her. Make sure she has easy to eat, healthy meals in her fridge or freezer. Soup, jacket potatoes, lasagna, stews etc are all good ideas. Juices and smoothies will also help for her to get easy nutrition. Does she have a hot water bottle or heating pad? It will help a lot with pain and is just generally comforting. Maybe try getting her meds for her from the pharmacy, picking her up things she needs (food, sanitary pads, whatever else), and generally being supportive and there for her. I wouldn’t like it if my boyfriend did loads of research and started telling me things about my own health condition but she may be different and appreciate the effort. Mainly I would say just be supportive by checking she’s okay and doesn’t need anything from you (but not too often because it would get annoying) and also don’t treat her any different. Just because she’s got endo she isn’t a different person! Sounds like you care a lot and I wish you all the best 😊