Is XOXO flirty or friendly?

Start with what the message is actually doing. If she's apologising, sharing a bit about her day, or asking a question, she's engaging with you as a person, and XOXO is just how she signs off warmly. If the message is three words about a time or place and then XOXO, the sign-off is probably habit or a reflex she uses with everyone.

Also check the history. Has she used XOXO before, and with whom? Some people send it to every contact by default. Others are careful and only use it when they mean something. If you have a few earlier messages from her, look at whether the tone has been warm all along or whether this one stands out. A sudden jump in warmth after a stretch of neutral texts means more than the same sign-off she always uses.

Most replies fall into one of three kinds, and each does a different job. The first is a warm match: you write back with similar energy, respond to the actual content of her message, and maybe add a small warm sign-off of your own if the history supports it. This works when she's been warm and expressive. Your draft should refer to something she said, not just to the fact that she signed off.

The second is a light, casual reply. It's short, friendly, centred on the plans or the thing she mentioned, with no sign-off and no pushing. This fits when the XOXO looks like habit. You can tell a draft is this kind because it reads fine to a friend and doesn't need a reaction. The third is a question reply: you answer what she said and ask her one thing about her day or the plan. That gives her an easy next move without forcing her to decide what the sign-off meant.

In all three, leave out any reference to the XOXO itself. Commenting on it, teasing about it, or asking if she meant it shows you're more invested in the subtext than the conversation.

Give it a day or so unless the plans are time-sensitive. If she replies warmly, asks you something, or picks up a thread you left open, keep going at the level she's using. If she replies with a short acknowledgement, that's useful too. She's keeping it low-key, so match that and let the energy stay where she puts it.

If you're still unsure after two or three exchanges, don't try to settle it by asking. Suggest a concrete plan or ask a question that needs a real answer. That will tell you more than any amount of decoding the sign-off. If she stops replying or keeps everything minimal over several days, the signal is clear enough. Let it go and don't send a follow-up that tries to reopen the question.