I like to think of "ser" as typically being used for more permanent things. To help you remember, use D.O.T.: descriptions, origins, and time. Other than for time, “ser” is always used for things that are more likely to stay permanent, things such as a person’s hair color, or in this case, how many languages they know.
"Estar," on the other hand, is used for locations and conditions (temporary conditions such as emotions and well being). I like to think of "estar" as being used for things that can change readily. Use the acronym LoCo to help you remember this (LOcations and COnditions).
With the example of Lorena, her not being bilingual is a description/characteristic. It describes her and is for the most part, a permanent characteristic (unless she recruits Duo). So just as you would say "she is blonde: ella es rubia," you would also have to say "Lorena has never been bilingual: Lorena nunca ha sido bilingüe."
It's not about whether or not it could change (it's an okay rule of the thumb but you'll run into problems when it comes to details).
Instead, it's about whether it's a characteristic of her (ser) or a condition she is facing (estar). Inherent vs. superficial, you could say.
Umlaut is the german term for the dots above the "ü". In spanish it is referred to as a diaeresis.
The dieresis is used above the u when the u is sounded in the combinations ofgüi or güe. Without the dieresis the u would be silent.
For example the dieresis in the word pingüino causes a "w" like sound. Whereas in the word guerra the "u" is not pronounced.
Es muy probable que Lorena sea de los Estados Unidos.
Q: What do you call someone who is fluent in 3 languages? A: Trilingual! Q: What do you call someone who is fluent in 2 languages? A: Bilingual! Q: What do you call someone who is fluent in 1 language? A: American!