Should I keep my mom at home or admit her to a nursing home?

I am so tired of having Mom in my house but I feel so guilty about thinking about nursing home placement. I brought her here to live with me because of an untenable situation where she was, but I've been really regretting it.
She is rapidly declining with vascular dementia but it still very much aware of where she is and what she can no longer do. In one breath she says it's time to put her away, and in the next breath she says she doesn't want to go to a home and live without her dog, who is in fact an anchor to reality for her. She used to give me such a hard time, told people that she did things to aggravate me because she thought it was funny, which only succeeded in alienating me and shutting down emotionally toward her. Now that she is less physically and mentally able to do things she has mellowed quite a bit, but I still harbor the resentments and am basically only going through the motions taking care of her. Am I being selfish for wanting to get my life back together? How do I figure out whose needs to put first - hers with her dog, me with what I want? I know this sounds like I want someone to tell me what to do, but really I'd like some input into how others have handled similar situations and how they have worked out for you.