Well, that depends on what আপনি mean. Nahuel ব্যক্ত it would be seven and a half years অথবা so. দ্বারা that time she will have aged to about 18.
So depending on what আপনি mean দ্বারা "how old will she be?" I have to ask if আপনি mean literally অথবা looks to be. Literally she will be between 7 1/2 to 8 years old. She will look like she is 18 and have the mentality and maturity of an adult.