Move-on. Sorry to be the bearer of bitter truth. If they haven't gotten back, they are considering other candidates. This is from my personal experience with the Modem firmware team in 2017. Having said that if they want you, they will make an offer the very next day - this is my other experience which I accepted and thus am with QCOM
It could mean many things i.e. I think it doesnt mean anything practically. I was a top scored candidate from several teams at once, and my official offer took weeks to be ready. HR ignored my email but hiring managers contacted me directly. So I communicated with them. I think it should be totally fine to talk to hiring manager if you have a contact. And another thing is I heard the recent HR workload is super high because of massive hiring/interviews. Maybe it is just delayed.
The person responsible for moving this along is probably OOO or maybe just forgot. So you could send an email to your contact and ask for an update. There's 2 things about the company culture. If someone is out, no one takes care of the work while they're gone. It just waits to get done no matter how many problems that causes. Also, you have to bother people several times before they will actually do what you ask.
I followed up with the HR twice in two weeks and haven’t heard from her yet. Thinking if I should contact the hiring manager or that won’t look good? I have to make a decision soon as I have another offer
If HR has not responded within the timeline they told you, contact literally anyone else that has been involved in your interview process and tell them you haven't been able to get through to HR and that you have another deadline.