is it healthy to stay up until 7 am and not go to sleep?

it can affect your kid's health which might make her more proned to getting sick

if your doing it on a constant basis it's okay but if it's irregular it's not, the body adapts the circadian rhythm to the patterns of sleep so when u wake up you'll have hormone set and ready to utilize energy, but it needs at least 2 weeks to adapt

No, that is not healthy.

You're the parent, so parent. There should be no need to chase your child around. You tell her when her bedtime is, and she goes (or there's a penalty for not minding you). You can't force her to sleep, but you can require she go to her room, get in the bed, and stay there. Cutting off computer access and TV access after bedtime, will also give her less thins to do (other than sleep).

that's not healthy for anyone

No, it's not.

Get a sleep mask, do light exercise b4 bed, go to bed at a regular time on a regular basis.

Eventually, your body/brain will catch on.

No screens 1 hr b4 bed. The blue light frequencies mess up your brain. It will think it's daytime.

I think it's fine if you're eating healthy and getting your sleep. If you're just not sleeping at all, then no it's pretty terrible. Your body is going to crash sooner or later.

One of my friends was insomniac or something, he had trouble sleeping seriously.

Now though something strange happened. He's constantly sleeping 10-12+ hours a day.