The fact that she shows interest in the toilet is great. This is the first step to what a friend of mine calls "potty learning". The pulling the diaper thing is probably not be a true indicater that she's ready to make the transition, but rather a typical toddler thing. Mine liked to do that and so did his friends at that age, but none of them were anywhere where near ready at the time.
At 15 months, it's probably a bit too soon for your daughter, but you can of course start introducing the concepts to her. Just try not to pressure her or feel down hearted about it. Her muscles and other physical aspects are probaly not there yet so be patient. Usually a child will begin waking up dry and this will be a good sign that maybe she's getting ready. Also, I don't know where her verbal skills are at but it really really helps if they can communicate their need to go potty. At 15 months, most kiddos just don't have the language skills yet.
Typically it seems that the sooner you push potty training, the more they push back or the longer it takes. It really needs to be their idea and they need to be physically ready which can be anywhere from 2 yrs to 4 yrs. It's a broad range of normal and just because your kid is early/late to pick up on it doesn't mean they're smart/stupid or that you're a better/worse parent. Also, once they do potty learn, it doesn't necessarily make your life easier. Au contraire! You might find yourself in every bathroom, port-a-potty or urinal in town (if you're lucky) at the most inconvenient times. Nobody tells you this. :)
I'd start very low key by giving her a potty book that you can read to her. Start reading it so she has an idea what the potty is for, etc. Let her come with you to the bathroom so she can see what you do. There are also books especially for girls (and boys). We didn't get a little potty but just one of those inserts for the toilet. We didn't get these for my son until he was a little over two and only at his insistence (it has to be their idea imo). He loved reading the book and would occasionally sit on the potty with his clothes off or on.
Early this summer we transitioned to underpants and this helped my son. We actually put him in these not to potty train him, but to help his horrible itchy prickly heat. He had been going in the toilet on a fairly consistent basis but not 100%. We decided to see how he would take things and over a week we had to be careful timing our trips outside the home, but to his credit we had no accidents. We've actually had very few which, i think, also indicates his readiness to potty learn. He also wakes up dry consistently (a BIG indicator that your child is ready to potty learn). Occasionally he would ask for a diaper and we always obliged. This is normal to and we just didn't make a big deal of it since we had originally figured he wouldn't potty train until next year anyway. I think the lack of pressure really helped too.
Keep in mind, my son will be 3 in Nov and he is only the second or so in his peer group to make this transition and certainly the youngest. I know many very very bright children who are older and have great parents who are still not doing the potty thing. It's ok. Like I said before, this is normal. They'll pick it up eventually, on their own and then you'll be making all the wonderful and frequent pit stops that we're getting to make.