How normal is this behaviour?

Since having had a real bad experience with bonding in the past I am now always super vigilant... so here is a scenario I noticed a lot lately.
Fluffy LOVES chasing Bunbuns around, what happens is she is laying down... as she usually does, she is extremely lazy and he's very playful. So he comes up to her from behind and nips/or licks... can't really tell.... her in the butt, then she runs off, they both run around the room like crazy a few times, then he stops, she looks back where he is, if he's not following her, she goes to him, puts her head under him, he grooms her with a lick or two, then back doing the butt thing, she runs off again, and so it goes on. It ends usually by her running into their pen and her going round the tunnel, looking out to see where he is, and when he doesn't follow her, she flops on the floor again. This is what usually happens, sometimes she does look a bit scared, but then she does keep going back to him, so maybe she's just super alert.
anyhow... today I noticed something different... a lump of her hair was pulled out. I haven't had that before with those two, so just want to be sure it's normal that this can happen when they play.

They are usually inseparable anyway, well most of the time, just like humans, they are not spending every waking hour together, but they sleep often in separate corners for a while, then I see them snuggled up after a while. guess when they had enough of being alone, who knows. And the lady who had them while the pen was build said you can tell how much in love they are, but when I see a big lump of fur I cant help but worry, so any advice is appreciated. They since have been grooming each other, eating together and all that, right now sleeping, in separate corners, but that's normal for them at this time of the day.

It more or less sounds normal - somebun may want to be more dominant? I would just keep an eye on them as it is fairly early days still.

Since 2 became 3 mine are very..exuberant at times. me & my OH are forever saying "they playing or are they fighting" - this is mainly Boo & Joey who rarely exhibited this behaviour before (occasional tiff when Joe goes all alpha male over food treats. i say treats, last night is was over cauliflower stalks:lol I think its more play, they get some binkies in there & touch wood have not hurt each other. Mouse on the other hand just moves straight out of the way. I've noticed now she is getting stronger she has started to throw the odd binky in when escaping Boo. Clever Mouse!

As Tonibun says I reckon its just keeping an eye on things but that's easy enough since we spend half our lives watching them:lol:

Thanks you two. Good to know it sounds normal. I watched them very closely this morning and she was the one who kept coming up to him when he wanted to sleep. he gave in in the end and he started chasing her... well I say chasing her, they were running past me and both were next to each other with Fluffy doing his binky run where he half runs and half binks. she then run off and hid in the corner... looking all, what I first saw as "scared" again, but now wondering if it's actually her just being very alert, since they are going at such fast speed they probably being extra careful not to bump into anything. I haven't seen any more hair being pulled since, nor before really, so maybe he just got a bit too rough playing yesterday, but will naturally keep an eye on them anyway. and so true re the watching them, never seems to stop, does it lol
Glad Mouse is getting stronger integrated too, I bet you're happy about that.