Sorry I didn't post in time to reach you before you visited, but I'm glad it went reasonably well.
Please try to remember that YOU didn't "take her out of her own home," dementia did. The disease is the enemy, not you. You are not bad, or a bad person, or a bad daughter, although you probably feel that way sometimes (I know I do).
As far as feeling badly about lying, rather than thinking about whether you're telling the truth, the whole truth, and nothing but the truth, think about what you are saying, how you are saying it, and the impact it will have on your mum. Then think about what the kindest choice for her is. Sometimes I do tell the truth to my mother, when I can, but mostly I lie, prevaricate, change the subject, leave things out, distract her, you name it, anything and everything to avoid the truth about some issues. I do this because the truth would upset her, she can't comprehend things well anymore, her memory is shot, but that emotional reaction stays with her, and I will do anything to spare her anxiety and upset. (She had crippling and heartrendingly distressing anxiety before going into her care home.)
I personally think that while we have to do the best things possible for our PWDs in terms of physical and financial well being (getting them medical care, making sure they are safe, paying bills, managing finances, and all the other things my PWD can no longer do for herself), we also have to do the best thing possible in terms of emotional well being, at least as much as we can. (Sometimes there isn't anything we can do.) In my case, that includes lying like a rug, being cheerful and upbeat, and avoiding distressing her as much as possible.
Sorry, that was a bit wordy.
Try not to be too hard on yourself. Easy to say, difficult to do. Somebody here needs to hand you the pointy stick that you use for poking the Guilt Monster in the eye, when it gets too close to you.
Also, something that helped me a lot when my mother first went into the care home, was to call and have a chat with the staff. My mother's version of what she did in the care home (sitting alone in her room with no meds and no people for days on end) and what she was actually doing (eating 3 decent meals a day in the dining room, talking to people, going to all the activities, making a friend, having her hair done) were very different! It also allowed me a way to start to get to know the staff, as I wasn't visiting at that time. (My presence upset her so much, I didn't visit her for a month or more after she moved in.)
It's a big adjustment, but it does get better with time. The relief of knowing my mother was safe, properly fed, and getting the proper medications, was huge (as none of those things were happening at home), but it took a long time and a lot of help to get comfortable with the idea.
I always take something with me when I visit--chocolate, biscuits, a book, even boring items like toiletries are always well received, so it never hurts to be bearing a gift!
Again, try to be kind to yourself, and remember that TP is always open! Very best wishes to you and your mum.