Good blood always shows itself ‧ en.wikiquote.org/wiki/English_proverbs
Good wine makes good blood ‧ Good wine makes good cheer ‧ www.famigliacecchi.it/en/news/10-italian-proverbs-about-wine/197 ‧
голубая кровь ‧ en.wikipedia.org/wiki/Blue_blood
I read this sentence to my friend who is a native speaker of Russian. She didn't think it was strange at all. She said doctors say in Russian "She has clean blood" or "she has good blood," to mean, "we ran the tests, and she doesn't have diabetes, [or whatever they were checking for]." She said doctors usually say "clean blood," but she has also heard "good blood."
It's typical for Russian to skip the equivalents of "to be" and "to have" verbs in present tense; the lack of these verbs implies present tense (or the other way around, if you wish). They must show up in past and future tenses:
I am fine = Я [есть, являюсь, пребываю] в порядке
I was fine = Я был в порядке
I will be fine = Я буду в порядке
She has the car keys = У неё [есть, имеются] ключи от машины
She had the car keys = У неё были ключи от машины
She will have the car keys = У неё будут ключи от машины
In this particular example, there is also a semantic difference. "У неё хорошая кровь" implies "her blood is good". If you say "У неё есть хорошая кровь", it will imply "she is in possession of good blood".
In Russian, clauses are generally separated by commas. You often see them before что "that", когда "when", который "that, which", потому что "because" and other conjunctions—even и "and" whenever it connects independent clauses. English does not do that.
Consider it markdown.
Now, this particular sentence does not use any conjunctions but it does not change the fact that "she has good blood" is a separate clause—a clause that details what 'I think" is about.