Has she been to a vet for an annual physical, yet? Getting a CBC each year is a good way to establish a baseline for their health/possibly uncover underlying issues that may arise over time. A fresh stool sample may also provide insights into some GI problems. Usually all that stuff is included in the yearly physical exam. If you bring her into the vet for the vomiting issue, the vet will probably want to do those labs, which more or less gets you the annual physical exam at a lower cost, depending on the vet (w/mine, if they're brought in for something specific, the exam fee is lower than the annual exam fee. If you get the most important labs done, it's sort of a loophole to get around the larger fee, if that makes sense. If money is an issue, at all). And, if money is an issue, you may want to google low cost vets in your area, who do it as a charity, more or less, or check w/veterinary schools, who will sometimes treat at a reduced price, while the professor either teaches or monitors a student w/an animal, sort of like dental schools. I've not taken that route before, but I've heard the option exists in some areas of the US. The low-cost one in my area has good reviews (Yelp may be a good way to locate one).
But yeah, first & foremost, monitoring/note-taking/scheduled meals (like every 12hrs 9am & 9pm or something) would be a good start.
Hope you find out what's going on with her - I wish you luck.