So I finally got this girl I've been fucking for a little while (we've met up 4 times so far, each time multiple fuck sessions) now to finally give me head. For the first blowjob she did it during foreplay but I didn't cum in her mouth, instead finished by fucking her. The next day we have morning sex and she then starts to suck me off again. After showing her how I like it and teaching her a few things, this blowjob felt a lot better than the first.

I made it pretty apparent (or at least I thought) that I was about to cum, but when I finally did she took her mouth off my cock halfway through me busting, resulting in a mess everywhere. She wiped her mouth and then giggled, and said "Now we really do need a shower".

I was kind of pissed that she stopped in the middle like that, but I didn't say anything and played it cool. We just proceeded to take a shower together and it didn't come up again. I'm guessing she wasn't expecting me to cum, and when I did it caught her off guard. What's the best way to go about telling her not to do that shit again without acting butthurt? Is this considered "bad behavior" that needs to be checked? Ideally I'd like to get her to swallow, but at the very least let me finish.