I wouldn't consider that cheating per se, but I will say that this is a non commitment to her existing relationship.

If it is a toxic relationship, be it due to herself or the guy; or an unhealthy one, she should leave. Not getting herself involved with the 'superior' while she is in a relationship.

While for the guy, he is probably experiencing the thrill of being able to obtain attention from the girl who had a partner.

Not saying that she should mend the relationship if she hasn't or don't want to; or it is wrong for the guy to pursue her, its the condition that they are in that makes the whole thing morally incomplete.

1 foot in or not, a guy should know when to walk. As for me, I would think that if this is indeed the situation, and the girl somehow 'seeks' an alternative outside of an existing relationship while being in one, I would then ask myself this:

- If she can do it to someone else now, what makes me think that if we have a rainy day one day, and she does this to me too?

As to your question of "Why are you treating me so good like boyfriend?" and then ghost him for 2 days+ then come back and find him again?'

It could be anything, it could be that she happens to reconcile with the boyfriend, and then after 2 days, the refraction period with the boyfriend's reconciliation period cooled down and she's emotionally available elsewhere again.

No, she does not need to.

What I am saying is that, it could be that the boyfriend was the one that reconciled with her; but it can also happen vice versa.

It does not need to happen regularly, but we can't simply rule out the other parties can take action and make changes.

Think of it this way. This is just one of the many possible simulated examples that can happen.

1. Boyfriend and girlfriend argues.
2. Girlfriend is upset, as the boyfriend offends her for the same reason again.
3. Girlfriend needs a place to vent, superior happens to be the listening ear.
4. They texts and exchange thoughts.
5. Superior feels attracted.
6. Boyfriend reconciles and have a road trip with girlfriend.
7. Girlfriend ghosts superior as she now reconciled with the boyfriend as she feels happy that she got the trip she wanted.
8. The pair returns from trip, girlfriend feels that the situation is slowly back to status quo.
9. Girlfriend reverts to the superior.

Again, this is just one of the simulations. It could be any other possibilities.

But if you dissect the situation, you may find previous responds of the girlfriend 'finding provider for her needs - be it emotional or material or physical' relevant.