How and when tell my Gf about her body odors

So, we are in our mid 20s and this is our first relationship. We got together a couple month ago and met the first time several months ago.

In this couple months, we started to be more intimate and I noticed that sometimes she had some odors. I kinda shrugged off this thing thinking it was normal after long days, but maybe it was just an excuse to avoid the problem.

Yesterday we went to a party and I briefly noticed it but in just some moments, and she told me before that she was sweating.

Now, I magically formed the thought that it is my duty to tell her, if she isn't aware of this thing. The problem is: I avoided this thing so much that I can't really pinpoint when and how I noticed it, so I can't really help telling her "I think that maybe you could possibly have this problem", I want to be sure that isn't just some occasion before embarrass her. At the same time, I don't want to ignore my duty too long, because we will not see each other for a couple of weeks.

I don't really think that she doesn't wash properly, I think it is more like a sweating think with an ineffective use of deodorant.

How and when should I tell her?