Lots and lots of moms use potties and stores sell them so there must be SOME use for them, but I am currently potty training child #3 and used to be a preschool teacher for 2 year olds so I have potty trained many. I think potties are gross and unnecessary! I never could understand why anyone would want to have a mini port-a-potty in their home when they have indoor plumbing!! It just seems so gross and unsanitary to me-- you have to clean and disinfect it every time it is used and when they really get into potty training they like to go constantly even if it's just a couple of drops. THEN, once you think you have them potty trained, you have to teach them to transition to the big potty... plus, if they only know how to go on the mini gross port-a-potty that you bought, what do you do when you are out in public??? OK, sorry for my crazy rant... I just have the cushy ring that sits on the real toilet. It has handles they can hold on to and keeps them from falling in for their first bathroom experiences. They love the whole process of pushing the stool over to the toilet and sitting on the squishy seat. For public restrooms, they are already used to the big toilet and the whole idea of the flushing and watching the pee/poop go down the drain. You can hold them so they don't fall in, or you can strip them and seat them backwards so they straddle the toilet facing backwards so they don't fall in. As for training her at 16 months, her interest in the potty is only one sign of readiness and there are many. If she is unable to hold it until she gets to the potty/toilet, you will be on a serious uphill losing battle for MONTHS of frustration, during which time you will end up switching back and forth between diapers and underwear,wondering if she really is ready, which is confusing as heck to a child. Or worse yet, you'll use those Pull Ups, which the only thing I have found more useless than them is a wipes warmer... but lots of people buy both of those things, so I think there are marketing geniuses who really are the devil, or many people just have money to burn and can't figure out what else to spend it on. Again, sorry for my crazy rant, but I find Pull Ups to be pointless and expensive. Diapers or underwear- pick one. My 2.5 year old has decided he wants underwear, period. At night, I put him in a "night night diaper" (a regular diaper) because we don't want his bed to get wet. Those will be gone soon, too, because he has been waking up dry most mornings. My sister had my 3 year old niece in a Pull Up at night for ages after she was potty trained until I pointed out that she was most likely staying dry through the night but peeing in her Pull Up first thing in the morning because why not? She has it on so why hold it and rush into the bathroom while she is groggy? So I saved my sister a ton of money she used to spend on Pull Ups by suggesting she test my theory-- she offered her daughter some sort of reward (sticker or something sweet) for every morning she stayed dry and low and behold she was able to get rid of Pull Ups within a week.
Good luck on the potty training. But I beg you to wait. There is no rush to start until she is truly ready.