Is it always a bad thing when a relationship moves fast?

Wayyyyy too fast.

I always tell single moms to keep guys away till it gets serious. If a parent bounces from partner to partner, those kids are gonna think that’s how relationships work and it’s a terrible example.

But if you both feel really good about it, make sure you go over as friends and keep your hands to yourself.

It usually takes about one to two years to truly get to know someone. All that sex so quickly after you meet someone is basically bonding you, and making you feel like you're in love with someone you don't really know at all.

Red flags

Fast means you will end up feeling you like that person until you realize that you hate her after few months. I have dumped many girls just because i moved on too fast and they fell in love and i thought i was in love too. But few months into the relationship its just too boring to continue it.

That is way too fast, a relationship should flow slowly like water, relationship in reality should be getting to know someone whether it would be hobbies and interests. I should know this because I made that slight dumb mistake with my current girlfriend I went a little bit too fast.

I would run a mile from anyone wanting to introduce you to their children after such a short period of time. I say this a mother. That's a big red flag to me that she's irresponsible and impulsive.

If you want to keep fucking the shit out of each other then great, keep doing it. No issues there. But don't go anywhere near her kids until you're fairly certain that you want to spend the rest of your life with this woman. That usually takes over a year.

(I'm assuming here that her kids are very young, because you've said she's 26. If they're teenagers then I would be slightly less cautious).

Meh.. Theres relationships that take it slow and don't last, I think the beginning does not matter its really about how you end. If you end up being together forever, really this won't matter

I think so, though obviously it has worked out well for some people.
Thing is i've had amazing chemistry with people from the first date myself, only for things to quickly go downhill when we start to know each other better the reason being it's common to show your best side at first, everyone does that. In the beginning most people aren't comfortable being entirely themselves yet.
A slowburn relationship is typically better because it's not born out of quick passion, but something real and stable. Instant chemistry tends to happen fast and fizzle out fast and there tends to be many intense ups and downs before you truly cannot stand each other anymore. But yeah again, there are exceptions.

In my personal opinion it doesn't sound like you've had a very serious relationship so far. Do you even know this chick? If you guys barely know each other it's enough of a warning sign that she's already willing to let you meet her kids, responsible parents are very very careful about introducing someone they're seeing to their kids since 1.there's unfortunately a lot of creeps out there who target single mothers and 2.because if it turns out to not work between the two of you it will also affect the kids and 3.because if one dates a lot they don't wanna keep introducing their kids to new guys because that provides an unstable home environment, confusion and makes you a bad rolemodel.
Hence I would be suspicious if I were in your shoes, sleeping with a woman a few times and then she wants to introduce you to the kids... Is she just really desperate for a stepdad to those children?

Get to know her first.

Fast can work out just fine. But the people involved have to have their heads screwed on right. They have to have learned how to make relationships work. They need to know how to deal with conflicts, negotiate and compromise and be willing to do so. Most importantly, they have to know how to communicate honestly and clearly and in a positive way.

And while I think I understand what you're feeling with this woman, your OP and comments make me wonder if that communication bit is part of your skill-set. You shouldn't be asking these questions of this particular subset of random internet fools; you should be talking to her about your feelings and your concerns. If you're not comfortable with making the leap into vulnerability by laying it all out for her, then I doubt if there's much chance this is going to work.

The existence of kids is a serious issue. If this doesn't just turn out to be an infatuation that's a huge blaze of passion followed by rapidly fizzling out, then you need to have some serious discussions about what role she sees you playing in their lives. Being a step-parent can be very rewarding, but in so many cases the appearance of a new man in a mother's life is the cause of huge problems for the kids, the mother and thus for the new guy.

Fast is not always wrong if things really line up.

I asked my wife to marry me about 2 weeks after we met in person. We did have an email/Skype relationship for 3 months prior to that though.

But, once we met... it did not take long to conclude that she thought and acted right according to my standards.

We've been married over 9 years now... and are very much in love.

If its right... its right. Just do a reality check and make sure its not just lust... What are the other things that attract her to you (shared interests, values, future dreams, etc...). Are both of you honest and have good character?

I wish you well with this.

Edited to add: While it is true that it takes years to know a person: Marriage is about resolving issues and conflicts as you learn about each other. It's not "they lived happily ever after." My wife & I had a rough year and actually spent 6 months in counseling to understand an issue. It took another 6 months to figure out how we would adjust our lives based on what we learned about ourselves and each other.

Marriage is a commitment to work out problems and issues... Those that have done so will tell you that its well worth it...