I wouldn't ask in the moment. Chances are if you're asking, it's because they are noticeably acting off, and depending on their level of insight they might not even be able to answer honestly, and if they can there's no guarantee they will.

Personally, I appreciate when people can tell me GENUINELY (as in it feels like an authentic vibe between close friends, not that fake bs from people I "know" (even "well") but the relationship isn't close) that I can let them know if something is too much or feels off.

Unaluna is kinda right though, are you feeling at all abandoned or rejected because of her being distant when you're not in person? You don't have to answer me, just think about it.