You are begging the question by assuming she isn't 15 in elf years, but that's not how any of this works. She might as well be 15. That's ripe for child bearing in the medieval ages. To me, she's closer to 60 because she isn't even sure if she's older than Jaheira who is in her 30s.
Oh look the nonce can't read. Let me help you with this. Here's the rules you fucking retarded nigger shit.
Going off of the official AD&D 2E rules used by BG 2 this is the following age range for elves. The first number is human and the number range is for elves using Table 4 from The Complete Book of Elves for AD&D 2E in years.
Human | Aquatic/Avariel Elf Childhood
1 | 1-5.3
2 | 5.4-10.7
3 | 10.8-16.1
4 | 16.2-21.5
5 | 21.6-26.9
6 | 27-32.3
7 | 32.4-37.7
8 | 37.8-43.1
9 | 43.2-48.5
10 | 48.6-53.9
11 | 54-59
It says on page 38, "Elves remain children for approximately 65-75 years. They grow slowly throughout these years, achieving a height of 4 feet at most." Thus, the elf is still in the pre-pubescent stage of their lives. If you disagree with the writing in the AD&D 2E rules then you're a nonce.
Human | Aquatic/Avariel Elf Adolescence
12 | 59.1-65.6
13 | 66.7-72.1
14 | 72.2-78.7
15 | 78.8-85.3
16 | 85.4-91.9
17 | 92-98.5
18 | 98.6-99
Continuing with the description on page 38 for adolescence, "At about age 75, elves enter adolescence. Whether male or female makes no difference; both sexes mature at roughly the same time and at the same rate." Adolescence is puberty.
A few notes here. Drow mature fastest out of all the Elvish racial subtypes while Grey elves take the longest to mature. The following table is the numbers for childhood and adolescence of those two compared to humans with the span of years for each human year of development.
Human | Drow Elf Childhood
1 |1-4.4
2 | 4.5-8.9
3 | 9-13.4
4 | 13.5-17.9
5 | 18-22.4
6 | 22.5-26.9
7 | 27-31.4
8 | 31.5-35.9
9 | 36-40.4
10 | 40.5-44.9
11 | 45-49
Human | Grey Elf Childhood
1 | 1-7.18
2 | 7.19-14.37
3 | 14.38-21.56
4 | 21.57-28.75
5 | 28.76-35.94
6 | 35.95-43.13
7 | 43.14-50.32
8 | 50.33-57.51
9 | 57.52-64.7
10 | 64.8-71.89
11 | 71.9-79
Human | Drow Elf Adolescence
12 | 49.1-54
13 | 54.1-58.9
14 | 59-63.8
15 | 63.9-68.7
16 | 68.8-73.6
17 | 73.7-78.5
18 | 78.6-79
Human | Grey Elf Adolescence
12 | 79.1-85.6
13 | 85.7-92.2
14 | 92.3-98.8
15 | 98.9-105.4
16 | 105.5-112
17 | 112.1-118.6
18 | 118.7-119
The table and rules are quite clear on how elves age in AD&D 2E which BG 2 uses. As such, Aerie would be roughly 84.5-99 years old for an Avariel Elf. She would be the equivalent of a 16-18 year old human. She is a teenager due to her growth as an Elf.
There ya go nonce lover. The rules that you ignored so far. So we've established you like preteen girls as you are adamant that Aerie is a preteen at the ripe old human equivalent age of 12 as an elf of 60 years. Do you happen to know math per chance or how to fucking read?