Thank for you for the additional information. Based on what you said, this is definitely a case in which the expertise and skills of a professional conservator are needed. A conservator will be able to identify what is original, what is a later addition, and what is a repair. The conservator will then be able to redo previous repairs as necessary, do new repairs, and inpaint any damage so it is less noticeable.
You can find conservators using AIC’s Find a Conservator Tool:
http://www.conservation-us.org/membership/find-a-conservator#
If you can’t find a conservator nearby, don’t worry – some conservators will accept objects by mail.
For future reference, repairing plaster is difficult. Like low-fired ceramics such as earthenware or terracotta, plaster is porous and soft. That means that the wrong adhesive could stain plaster or even damage the surface. Although a plaster wall can be patched with more plaster, this is not appropriate for art – because plaster is porous, newly added plaster will lose moisture and won’t be very strong. Therefore any repair on a sculpture made with plaster won’t be strong enough, especially not for a structural repair. On the other end of the strength scale, epoxy is much too hard to use on plaster and could cause staining. As plaster is usually white, it is very important to choose a conservation-grade adhesive, that is one that won’t yellow over time.
This sculpture is especially complicated – the adhesive I would normally use for a plaster sculpture is prepared using acetone, but in this case, acetone might damage the enamel spray paint and the nail polish.
For more general information on plaster, see CCI’s note on the care of objects made of Plaster of Paris:
https://www.cci-icc.gc.ca/resources-ressources/ccinotesicc/12-2-eng.aspx
Thanks,
Elizabeth