My D20 was in a similar situation, but she decided to start a new FL tract in 10th grade, so she’ll have 3 years of Spanish and 3 years of Mandarin. Her school requires a language every year of enrollment. She has been told it probably won’t be a problem since (1) the fourth year is “recommended” and not required AND (2) three years of two languages isn’t necessarily a bad thing. We were told by her counselor and the two LACs she’s asked that even though she completed high-school “Spanish 3” that colleges tend to look at the middle school years a little different, and that it is actually her willingness to complete three years of Mandarin in high school that they will look favorably upon. Some of that may be because the language is Mandarin, though, which may be looked at differently than French or Spanish which so many kids take. Also, at least in our school, the fourth year of Mandarin is AP level (compared with the 5th and 6th years of Spanish). I would have your DD suck it up and take the fourth year of Spanish.