A double major in CS or engineering and business does not seem like a good idea. First, it will look like she is just looking for job prospects, rather than a subject that she actually has interest in, if she indicates that on applications. Second, the number of non-overlapping credits for these majors can make it difficult to fit both majors into the number of credits that one takes over four academic years. Third, some engineers believe that a new engineering graduate with a second major in business or large numbers of business courses may be thinking of engineering as a stepping stone to management, rather than engineering as something that s/he likes to do.
http://www.universityofcalifornia.edu/infocenter/freshman-admissions-summary indicates the percentage of students admitted as frosh for 2014 with HS GPA range of >= 4.20 (assuming that unweighted 3.98 with many honors and AP courses gives 4.3-4.4 weighted-capped GPA) at each campus.
43% Berkeley
93% Davis
98% Irvine
56% Los Angeles
97% Merced
99% Riverside
88% San Diego
91% Santa Barbara
97% Santa Cruz
However, CS is a popular major, so it may be more difficult to get in as a CS major than generally for a given campus. At Berkeley, a prospective CS major may apply as EECS (significantly harder to get in as a frosh) or L&S (more typical admission selectivity, but then must get a 3.3 college GPA in CS prerequisites to enter the CS major). Engineering majors or engineering divisions may have similar impactions. Undergraduate business is only offered at Berkeley, Irvine, and Riverside among the UCs.
Probable estimated difficulty of admission:
Berkeley – low reach for L&S, reach for EECS
Los Angeles – reach assuming engineering division (where CS is)
San Diego – low match for the campus, possibly high match or low reach for admission to impacted majors (see https://students.ucsd.edu/academics/advising/majors-minors/impacted-majors.html )
others – near safety for the campus (but impacted majors may be more difficult to gain admission to) – unlikely to be shut out if she applies to several of them
Some campuses may admit to the campus but not an impacted major. Be sure to check on the difficulty of changing into the impacted majors after enrolling. If it is difficult, you may want to do reach/match/safety assessments on the likelihood of admission to the major at the campus in question.