Hey, just to let you know, using "SWIM" or anything like that to avoid self-incrimination is actually against the rules on Bluelight, so you'll probably want to edit that if a mod doesn't get to it first.
As I'm sure you're aware, psychedelics can cause unpredictable thoughts, feelings, behaviors, etc. but it's all part of the experience; take the good with the bad. Anxiety during the come-up is common, but once the effects begin, this typically goes away. Of course it's possible to get anxious or experience other negative emotions once you're peaking, but it tends to be situational and not based on any legitimate threat. You could also always have a benzo ready if you feel the anxiety may lead to your girlfriend having a negative experience, but it should only be used as a last resort since it will dull the trip.
This is just a personal opinion and a purely hypothetical situation, but I think one of the worst things you can do if you notice someone having a difficult time is to ask "are you okay?" It's a thoughtful question under normal circumstances, but it may cause that person to overanalyze the meaning behind it, "am I okay? why would I not be okay? what does okay even mean?", stuff like that. A better solution could be to physically embrace or comfort the person, let them know you're there and everything will be fine.
Anxiety from weed is not necessarily an indicator that someone will get anxiety from LSD since drugs affect people in different ways. What substances has your girlfriend experimented with in the past? If she's tried other psychedelics before, she should have a decent idea of what to expect, but experience with things like cocaine, opiates or alcohol which don't have many similarities to LSD probably won't make much of a difference in the outcome of the trip. It wouldn't hurt to have her read up on LSD a bit to address any questions or concerns she may have. In any case, mindset prior to ingestion and physical setting will have more of an impact than any psychological or physiological effects other drugs have on an individual. It sounds like you will be in a safe place and won't have to attempt to appear sober or anything, so as long as you're both in a positive mood, there shouldn't be anything to worry about.
I would recommend only giving your girlfriend one hit just to see if she reacts well. Most people can handle one hit just fine, but you never know. I don't mean this to sound offensive, but it is something that has occurred many of the times I've used psychedelics with girls, whether a girlfriend or just friends: at some point, they have a little emotional breakdown, usually over something very personal that has been intensified by the drug, and it can be difficult to handle in the moment. Bear in mind that females tend to show emotions more overtly than males, and it's most likely nothing to be overly concerned about. The following applies to anyone, male or female, but some people need time alone to process their thoughts; be respectful and don't take it personally if your girlfriend needs to lie down in another room or something like that.
As far as things to do, the possibilities are endless! It may be helpful to have a few things roughly planned out, but keep your options open. It's easy to change your mind in the midst of a trip, just go with whatever happens. Is the condo actually on the beach, or just close enough to see the waves? A walk on the beach sounds like it'd be excellent as long as there aren't too many people around and it's not too far from your home in case you need to get back quickly for whatever reason. I don't particularly like watching movies very much during a trip, especially acid. It requires too much attention and can get confusing or frightening which may influence your trip. Above all, there are plenty of other things to do besides watch movies, you can do that any time. If anything, save it for the comedown.
I like to draw a lot when I'm tripping so having some notebooks and pens (or whatever your preferred medium) would be cool if you're into that kind of thing. Music is pretty much crucial on psychedelics for me. There are plenty of resources for "trippy" music, so I won't go into it too much, but anything you listen to sober will likely sound that much better. Don't be under the impression that you have to listen to psychedelic music just because you're on LSD, either. Some of the best experiences I've had listening to music on acid have been with artists I wouldn't have really considered to be good for a trip. There's something to be said about the sounds your mind is capable of producing rather than what is already there in the recording. You'd be amazed at how incredible simple or minimal music can sound.
SEX!
That's all for this little novel I've been working on over here, so most of all, have a fun and safe adventure on your birthday trip
