Relationship question (sorta)

Reddit, I come to you seeking advice; My girlfriend and I 23M/23F are long distance and have been dating for about 16 months. We are from the same city, and see each other whenever she comes home. We have been long distance the entire time we have been dating. I drive about 5.5 hours to see her once or twice a month. She is diagnosed with GAD, although I think an OCD diagnosis might be more accurate (not important for the story). She is on Lexapro to treat it.

She bumped her dosage up significantly from the dosage she had been using for years a couple months back, and though I didn't recognize it immediately, she's been a different person since. I haven't noticed a difference in her anxiety, or at least in the frequency of it, and she seems to be completely unaffectionate. Every time I've seen her for basically the last 6 months (changed dosage 6 months ago) I've come home miserable. She even said over Christmas that "our relationship doesn't seem to have any passion anymore". I was to the point where I was at the point of no hope and was planning on breaking up with her when I went to visit her next.

2 weeks ago, she came in town for a week, and I avoided her for 4 days (primarily due to work etc), then spent most of the day F/Sat/Sun with her. She forgot to take her Lexapro for 2 days and was back to the girl I fell in love with.

I can't figure out if her difference in attitude could be due to her stopping her meds temporarily, or if it was merely circumstantial.

If it could be a side effect of her coming off the meds temporarily, is this a conversation I should have with her, something I should ask if she is willing to test next time I see her, etc.

Frankly, her lack of affection could also be our relationship coming to its natural conclusion, so I am trying to get the thoughts of some people who have experience with this particular medication before I simply dump her, as I am very much so in love with her, but also very unhappy.

Anyways, cutting this off before the post gets too long, feel free to ask any clarification questions you have, and I'd appreciate y'all's insight.