I recommend floor time (tummy time but any floor time too) whenever possible rather than being in push chair, bouncer etc and talking to her about everything. Playing with toys together, singing songs etc is all great too, when you can't do those things though just include her in what's happening, describe what you see what you are doing etc.
I don't think you should be feeling guilty about her not having as much one to one time, there are benefits of her having an older sibling to watch, copy and learn from too. and it sounds like you do get one to one time. Let the guilt go and just enjoy your time with both your children as much as possible. x