Ladies - flirty texts question

Women are hard to figure out at the best of times, so I'm writing this to see if some of you girls can shed some light.

For this past week I've been doing a lot of late night messaging with a girl I know. The lady in question lives with her partner and their two young children and I assume they are happy..??

Some of the messages have been quite flirty, the flirtyness has mainly been instigated by me but she seems to reciprocate with the usaul winky smilies etc.

We've had talks about the movie fifty shades, where I would say something like "I'll put her over my knee for being naughty" (part from the movie) and she would reply with "as long as it's just your hand and not the whip lol"

Yesterday she sent me before and after pic of her new haircut asking for my opinion (she's not really the selfie type).

Now if she was single then I would be fairly confident that she likes me but as she's in a relationship with children I don't know what to think??

Is it just 'harmless flirting' on her part or is there more to it?