Question: around what age do female bengals go into heat the first time? My girl is about 8 months old right now.

Entirely depends on the girl and the environment.
If she's with an intact, fertile male she's likely to go into heat sooner.

It can happen anytime between 4 months and 14 months; though I would say 6-9 months is the normal range.

My girl went into season at 4 months, I had only had her a couple of weeks, it was a shock for me as I have not had a female cat before, my 4 year old male cat didn't know what was going on, his quiet life was totally disrupted, for 4 years he was on his own then suddenly this noisy screaming female is brought into his house.
Luckily I didn't have to wait long to have her spayed, the vet did it while she was still in season, life soon quietened down after that.

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Clare
Magic (brown spotted boy born 31 March 2012)
Pearl (seal Lynx Point girl born 1 October 2015)
Bristol, UK

OntarioBengals is correct. It varies with each female. But, generally, you can expect the first heat after 6 months. But, it can happen sooner, as Clare has mentioned. Are you planning on breeding your girl? If not, then it's best to have her fixed before she goes into her first heat.