Yes it is normal for it to be. Feminine discharge can be from white to a light yellow, it depends on many different factors (i.e. time of month, certain activities, even what she eats can make it more yellow then white). Anyways, it is normal and you should not be grossed out. Definitely not p*ss...
yeah it's normal for discharge to be a bit yellowish. if you're noticing yellowish stains on her panties and wondering what it is, it might also be period stains washed over and over and over. Mine tend to get a brownish/yellowish and it looks rather unpleasant, haha, but I know it's just blood.
the discharge itself usually isn't yellow, but the underwear usually stains that way.
Yes, it definitely can be. the discharge itself isn't usually yellowish, it just depends on how long it was in the underwear, how old the underwear is (aka, how many times has she gotten wet in them) and stuff like that. I've never p*ssed my underwear, but some of them are a little bit yellowish.