It had to be pretty much straight after graduation. Elena was still a schoolgirl only two months before FFVII began.
Well when are graduations usually held? It's December at the beginning of FFVII and she was working at a bar during the fall. Maybe she graduated at the end of the spring semester and then started working in the bar. Maybe she wore her school girl uniform while doing so because she got tips from guys into that sort of thing. She chose to make the school uniform her work uniform and keep her hair in pig tails because the school girl looked worked for her, and if any customer got too handsy she knew she could break their face.
In Re-Tseng's age, my head canon has him as 10 years older than Aerith, so he was 17 when she escaped at age 7. Which makes Tseng 32.
I think with age difference the "creepy" factor depends on circumstances. A 32 year old seeking out an 18 year old because they are 18 in order to prey on their inexperience is predatory and wrong. A 32 year old who happens to meet someone who happens to be 18, and likes them
despite the age gap is different. An substantial age gap, especially when the younger partner is very young, can certainly be a sign of a predatory relationship, but I don't think that's always the case as long as the younger partner is old enough to consent.
Elena is an adult by our world's standards, and possibly more-so by her world's standards. Considering you can join the army at 14 in this world, 18 is probably considered well into adulthood.
@ Octo
I suppose part of the reason boss/employee relationships seem particularly problematic to me is that my profession demands ethics training and one of the points emphasized is do not get into personal relationships with clients or colleagues. (Basically, the big rules, do not reveal confidential information, do not act against your employer's interests, do not mix professional relationships with personal relationships).
The reason an employee/boss could be problematic in general is the boss is in a position to take advantage of the employee. Of course, that's not an issue here since Tseng isn't going to sexually harass her or demand she exchange sexual favors for advancement or continued employment. I also think Tseng could compartmentalize enough to treat her professionally, so he shouldn't favor her or let his feelings for her cloud his judgement.
However, it's still a complicated, questionably ethical relationship because as her superior it's Tseng's job to guide her, and discipline her as a Turk. Having personal feelings could cloud or compromise Elena's judgement which puts her as risk. Essentially, it's Tseng's job to take care of Elena and he should consider whether dating her is in her best interests.
Not that I dislike the relationship. I ship it. I just think that Tseng has difficulty separating his personal feelings from his professional responsibilities.