i think she is too young to understand rejection or really get what's going on, so i don't see the harm in doing some photography or print work, so long as she seems to enjoy it (likes being in front of the camera, smiling, etc) when a child is that young, the parents decide everything for it, and if it's okay with you that someone takes photos of your daughter and the photo is used in a catalogue for baby clothes or whatever, then it's completely up to you! again, i don't see the harm, and she definitely won't remember anything from it later in life or really understand it at the time.

i would take her out of it once she got a bit older though (like 4-5, when she can understand and remember what people say about her) she may not be tall or thin enough to continue on modelling as she grows, so it's hard to judge now.

if she comes out and expresses interest in it later on at an older age, then it's up to you and her whether she can start doing it again, and consider the problems that you mentioned. like others have said, it's up to you to help her build confidence and self esteem, and if you do choose to continue her in modeling, to make sure she fully understands that not booking a job does not equal not good enough.

at 15 months though, worrying about rejection and eating disorders is a bit overkill. you have a beautiful daughter, so i would say go for it!