I contacted my friend to obviously tell her I was pregnant and that I need to move and I couldn't afford to give her all the money at once. Now this is where th problem start.
You were only 14 weeks pregnant. 
You would have had months to carry on working full time and absolutely no immediate need to change the arrangement. What a cheek you had to just expect her suck it up (with high levels of credit card interest) while you swanned around looking at bigger flats and spending HER money on buggies and babygros.
she was demanding I pay half and half which was not possible for me
Yes it was. You chose to make her wait while you prioritised other non-urgent things. To be frank I get the impression that even if you hadn't been PG there would have been some other 'reason' why it was 'not possible' to pay her back exactly as agreed, because you sound flaky and entitled.
I offered to pay £50 a month. She refused because she wanted all of the money because that's what we originally agreed.
If I can see no good reason for the original arrangement to have needed to change then I imagine she saw no reason either.
No, she wouldn't accept the money I offered and then blocked me so I had no way of paying her back
What absolute nonsense. Every time you got paid you could have put the £50 you could manage in an envelope and posted it through her door. That's what any decent person would have done. You don't sound like you tried very hard to do the right thing.
To who said I would have a year of payment saved. I did start to save the payments, then went on maternity and my wage dropped. Had to wait for working tax to sort my claim and needed to pay my rent, now I have no savings.
So you had some of the money put by but because she was still angry with you, you decided to spend it yourself instead of paying back what you could, when you could. Nice.
I understand what you guys are saying I've had a year to start saving, but it's not always that easy.
Yes it IS that easy. £250 isn't an awful lot of money when spread over a whole year. From last October to now it's about £4 a week.
I did have savings, however paying my rent became priority......it wasn't spare money, my rent took priority. A roof over my daughters head. That's not an excuse.
Eh? 
If you had savings then you should have given them to her in the first place. If you needed that money to pay rent then it's not 'savings' is it? Do you get housing benefit now? If £250 has really been that hard to find then I would guess that you weren't on a huge income even when working and I imagine now you will be getting HB for your rent, yes? So your rent is covered. Yes? Or no?
My daughters dad hasn't helped me at all, and I've had to do it all myself. I hardly bought anything brand new so that's not why I don't have any money.
That is your problem not hers - she's not a charity. Get your CSA payments sorted.
And for people saying turn up at her house etc, she refused to take the money I offered, I didn't want to turn up at her house and cause more issues because I wasn't invited.
Pathetic excuses again. You didn't need to see her or speak to her. You could have just put cash through the door with a letter of apology. You could have done that when this all first happened, in five lots of £50 if that was what you could manage.
I'm also not trying to make excuses. My situation changed.
Your financial situation did not need to change one iota until you went on maternity leave. You didn't do that at 14 weeks pregnant. Stop making excuses and stop insisting that you are not making excuses. Please. It's pathetic.
I wanted to know if I should message to offer her money. I do miss her as we were friends for such a long time, but the priority is getting this money back to her.
Why now? Just because she's unblocked you? So when you were blocked she didn't deserve for you to make any sort of effort to pay back? I am confused as to how your mind is working over this.
But in answer to the question, no you should not 'message her to offer her money.' She will probably tell you to stick your money up your arse and you can feel all morally superior because you 'tried to do the right thing' while still doing nothing at all.
Don't offer her the money. Just put pay it, FFS. Put it through her door. If you can do half now and half in January then just do it.
And learn a lesson from this. don't borrow money from friends again. And I hope she has learned not to lend it, at least for daft things like holidays and not unless she can afford to never see it again.