Reading the OP I cant add it up to 6k per month, she goes what 5 times in the first 10 days and then once a week, that is about 8 visits, one of which was 6-700 but that was more than usual. A bag of fruit, no more than 100 baht, incense as cheap as chips, what is she putting 500 cash in or something, way too much. OP are you just lonely and bored when she goes, go with her, put 20bt in the box. Shouldn't be much over 100 per visit combined I reckon. Most of the people at this village put in 20 in the box and a coin in the bowl that comes around, no money directly to the monks. On big days people put other more expensive offerings out, and maybe some cash on the banana tree but overall its never put any strain on my finances. The issue of whether you can buy merit is one for another debate, but my position on small donations is that the wat is a community facility, it costs money to run and as part of the community I don't mind making a small contribution

No worries OP. The girlfriend probably made a deal with the spirit that if she met a man of her dream, she would go to the temple and give certain gifts. I doubt it will continue after a few trips.