Just putting this out there, I grew up in a single parent family with my mum. But I think (particulary as a girl) I would also have been quite upset to find strange people in my parents bed. Probably more so if I had lived with my dad. You don't want her growing up thinking casual is the norm so I'd be careful when it comes to your little girl.
Having said that, my dad left when I was 7 and I havent seen him since (now 18), so big ups to you for sticking by your kids! :thup: