You don't need to SWIM here, you're already anonymous
Is the blotter from a reliable source, been reagent tested, already been taken from the same batch by someone you know?
How near in proximity are your friend & girlfriend going to be when you're typing with them?
I'm sure you'll be absolutely fine and I've enjoyed many a solo trip, but for the first time, I personally would have someone around or nearby who understands what you may be experiencing, & can be there if you need support, and/or a friend who's tripped before, to do it with
I understand that neither of these options may be available or indeed wanted, but I can't imagine my first few trips being the positive, amazing experiences they were without the people I did them with
Whatever you decide, stay safe & enjoy the ride