Congratulations on your new baby!
From your post you know exactly what's going on here - she's getting OS and (possibly) OT, and this is completely normal for her age. Getting her sleeping in the crib is brilliant at this age (really amazing) but with a preschooler around you can't rely on being able to do that. So you need to adapt - plan to use the sling, plan for buggy naps, plan to feed her to sleep etc. My experience, and the experience of a lot of parents on here, is that when the second one comes along, you need to just do what works, it's a matter of practicality. For now, you need to be minding yourself, enjoying your baby, paying attention to LO1s emotional needs, and definitely not getting stressed about LO2's naps! Follow EASY in terms of rhythm, don't beat yourself up if you're feeding to sleep (it's good to have a secret weapon, something that works when she's all riled up), and definitely don't imagine that you'll get every nap in the crib with your preschooler to manage too.