Re: My 15 month old refuses to eat!
Have you checked to see if she's cutting her molars? Between 12-15 months, it's perfectly normal for a child to stop wanting to eat, due to teething. Molars can be rough on some babies! You might not see teeth coming in, but if she's drooling a lot more than usual, chewing on random things (more than usual baby chewing), refusing to eat.... those can all be signs that molars are coming in.
Ibuprofen and/or teething tablets work wonders on a teething baby's appetite (just give it time to kick in before attempting to feed again).
Frozen peas are an excellent snack for a teething baby. The cold and hardness of the peas are soothing on sore gums, and of course, it's a green vegetable of sorts. I also like putting cheerios into the fridge and serving them cold.
Also, I wouldn't give her a plate at all. I'd put just a handful at a time (or less) on the table or tray. Way less messy that way!
As far as your older child, I would guess she likes being spoon fed, because it means more time spent with you. Try taking turns with her. You feed her 2-3 bites and then give her the spoon for her turn to feed herself 1 bite. The trick is, don't really give her a lot of attention while you feed her.... act completely uninterested. Have a book opened or the tv on or the computer in front of you, and pretend to be more interested in that. But when it's her turn, praise her like crazy! Tell her how big she is, and how she's not a baby like her sister, and how proud you are, and.... well, just really go overboard with it. Then take the spoon back again for your turn. Feed her 2-3 more bites (totally preoccupied and uninterested) and then give her another turn for 1 bite. Again, go overboard with the praise. Do this for a couple of meals, increasing how many bites she is "allowed" to do by herself, but don't give her full control for a day or so. Pretty soon, she'll by dying to show you that she is big and can do it all by herself!