How to invite girlfriend

Hi,

I met my girlfriend online last November, we met in January and in April in different Asian countries. We both would like to move forward and move together so that we could see how would we work together long term before committing to marriage.
I'm an EEA personnel living in the UK for 6.5 years and I'm a self employed. I'm earning more than enough to support both of us for her visit. We'd like her to come for around 6 months. Would a visitor visa be a good idea, or do we need to choose something else. Also, I would be her sponsor (not the sole one, as she is having a girlfriend in the UK as well), what should we state as a reason for her visit?

Would appreciate any ideas or insight...

Many thanks for reading!

Question not related to the topic of this forum.
And the answers are obvious : there is no other visa other than the visitor's visa. She will get 6 months in all cases.
I am not sure about having 2 sponsors. It might confuse the application.
Reason of the visit : Visiting boyfriend.
She need to prove that she will be back to her country after (education, family business). Without this she will not get the visa especially if you say she might stay if everything goes well.

Sorry I was wrong
this is the appropriate forum

The reason for the 2nd invite is to show that we have prepared for contingency (in case things weren't going well between us or I for whatever reason cannot support her any longer), she has a safe place to go, and friends could help her. Bank statement shows that there is enough money at her disposal to buy the return ticket in that case.
She doesn't really have economic ties to her home country, albeit her family ties are pretty strong, since she is living with her parents and as they are aging now, she is looking after them (in her absence it will be done by her sister). I don't know whether that will suffice though...
Thanks for the response so far!