I am a heterosexual male.

I've been with my girlfriend for nearly 6 years, and recently she's had this conviction that I'd gay and the whole relationship has been a lie.

She found a profile on a gay dating website which has the following information (and nothing else):

-My age
-My location (city)
-"Has a girlfriend" (not out-gay)
-"Into computers" (I'm doing a degree in Comp Sci).

She thinks that because this matches my description, it must be me, and this "proves" I'm gay. She went through my password manager looking for "evidence" (Of course, she found nothing). She also went through my emails.

She goes through my texts and emails on my phone looking for "evidence" that I'd having a second relationship with a man, or men.

Is there any way I can "prove" I'm not gay? (Obviously being in a loving relationship for 6 years isn't enough)

EDIT: Both aged 20. Nearly 6 year relationship.

EDIT2: When I asked her how I can "prove" I'm not gay she said I could propose to her.