I'm sorry to hear that your girl is having this issue. During the heat cycle hormone changes may cause a dog to vomit, one also must keep in mind that dogs in heat can be prone to uterine infections and the like as well (keep an eye on temerature and note if this continues). That said, being that she has this crusty area that you have described on her side, the vomitting may be due to this. Reactions to insect bites or stings can also cause this to occur. Clean the area with a saline solution and consider giving your vet a call to see about giving Benadryl (dogs with certain conditions should not take it). If her symptoms continue, or worsen, consider having her seen. I hope she's doing better soon.
No problem. Even if she is inside, house insects like spiders can leave behind a crusty scab along with vomitting. Also, mites, reactions to new shampoos/products and so on can lead to this. There are harmless cysts that can form as well and when scratched, they may leave behind an area as you have described. These can become infected and sometimes require an antibiotic. I hope she's doing better soon, they're a great breed.