I'm a lone parent with two DC 16 & 18. My DC have had a stepmum for roughly 9 years now. She treats my DC well, always has done, and that is all I ask.
She and I get on well on the rare occasion we see each other, we even stop in the street to talk if we bump into each other. When my exes mum died they gave me and my dd (ds didn't want to attend) a lift to the funeral and later we went back to my ex sil's for an informal 'wake'.
This may have been made easier by the fact that, looking back, I see that I'd started emotionally detaching from my ex before the relationship officially ended. Also the DC's stepmum and I used to work in a pub together and were for a while friends, although that friendship had 'slipped' a little after we both stopped working in the pub but we are still friendly.
Although I'm not a stepmum (or bonus as you prefer) myself I admit to lurking on here because I like to see the other pov. To try and understand things from the 'other side' for want of a better term.
That turned into a bit of an essay
wasn't meant to be but I hope you take it in the spirit it is meant
.