The pertinent question is, did she pay for all that to impress her boyfriend or was it done out of love/fondness for the little boy? If it's the latter, she should consider it a labour of love and allow the arrangements stand. However if she did it to impress her boyfriend... If she were my friend, I'll tell her not to cancel anything but she should consider it a "bowing out" gift to her boyfriend. Some sort of farewell or send off, if you will. That would be an apt punctuation to a defective relationship.
She has no business being in a relationship where a baby mama still holds that much sway over the baby daddy. If indeed the baby mama has moved on, why would she care if her baby daddy's girl, a live-in lover, would be present at the party? If your man can't control his baby mama and seems to put her feelings above yours, WTH are you doing dating and playing house with him for? Before long, baby #2 would be on the way, courtesy of your man. It's never advisable to play house with a man who hasn't put a ring on it.
In my opinion, a REAL man should be able to thug it out and pay for his son's birthday party expenses and completely leave his girl out of it. At most, she can get his son a gift if she's so inclined. If he's low on cash and feels compelled to "collabo" as per funds, the cash collaboration should be with the baby mama.
I'm afraid your friend seems to be majoring in the minor. The least of her problems should be the cancellation of cakes, clowns and party treats. The only cancellation she should concern herself with is that of the defective relationship she's in. Who runs to retrieve a pot of soup when a house is on fire? Misplaced priorities.
