How to approach my girlfriend about her sending me TikToks, rather than discussing the issues at hand

My girlfriend has called me stingy, but I call myself financially conscious. Today, she sent me a TikTok, featuring a girl who was visibly upset, with the caption, "when he's flipping out about paying for your guys $20 in n out meal but your ex literally would drop a bag every time you went out."
The comments only seemed to reinforce this. Comments such as, "like twenty dollars bitch stop," "Imma go bak," "Literally ?,? ?I miss him,? ?2 real tbh," etc.
We've been dating for about 18 months now. She makes little comments about it from time to time. I asked when we initially started dating about how she felt about "rotating." The idea being: I pay for this date, she can pay for the next, regardless of the total. If this was a big issue, why not bring it up initially? Instead of talking to be about it, she complains and reposts and sends me these likloks. Additionally, whenever I try to bring up a touchy subject that needs to be addressed, she shuts down and goes home. No hug, no kiss goodbye.
Any advice for a young man in his early twenties and his girlfriend the same age? Questions on further detail are welcome. Thank you.


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