She is gorgeous and so is your rottie - good on you for adopting them both! A lot of dogs in a new environment have tummy troubles - takes a couple months sometimes to settle into new food, routine, etc. but this normally seems to come out the other end as really loose stool or diarrhea. Vomiting, I think, is potentially more serious, and if you think there could be blood, I would definitely go to the vet, because better safe than sorry. It will put your mind at rest to take her in, and if she had been dosed with pepper spray (what's the story behind that, by the way?) that could have had some bad effects on her eyes, lungs, nose, intestinal tract, etc - I would want a vet to look at her because of the pepper spray even if she wasn't vomiting. That is potent stuff so maybe ask the vet to rinse her eyes out if they do that?
Again - she is really beautiful and I love your rottie (they are my favorite kind of dog!) and hopefully they will be best buddies for a long time! Keep us posted