I know you've updated but if by any chance it's your partner pressurising you into this then just remember, it's your body and if you don't want a termination don't have it.
There will be ways to make it work financially.
Your promotion at work is a temporary situation to cover a mat leave. It will end with the return of the current post holder. If her baby is already here she'll be back around the time you'd be ready to have your baby. At my workplace most people don't take the full year. They take between 6 and 9 months to avoid being without pay. You wouldn't necessarily have to take a full year off either, and even things like KIT days bring in extra money when your paid leave runs out.
If your daughter is two now she will be close to three or three already when baby would arrive. You could look after both on Mat leave, reducing childcare costs and on your return she'd be eligible for free hours. A baby would most likely be easier for grandma to cope with than a 3 year old.
If you use your free childcare hours carefully, as well as annual leave, parental leave (that includes DP too) grandma won't need to look after two kids. Childminders can be a cheaper option than nursery too so look into that.
Babies don't cost much in the early stages, especially if you're able to breastfeed. Second hand cloth nappies can also save costs. Hopefully you'd still have equipment left from your daughter and some hand me downs too but there are also charities and baby banks which give out free baby clothes and equipment.
Children can share a bedroom. A baby could co sleep in a next to me type cot initially then move into the same room as sibling. Even at 6 I've known opposite gender kids to still be sharing, usually in bunk beds.
There will be ways around it financially and it's also easier to take the career hit now when you already have a 2 year old and are in toddler stage then be going through it all again in your 30s.
Anyway, that's just in case you aren't sure and there's pressure from your partner. I'm only saying it because from my own experience, abortion regret is a real thing and there's very much a "if I could turn back the clock" feeling.
I totally agree with this;
Speaking as someone who’s also prone to think “What should I do” rather than “What do I wantto do”, I urge you to forget what you think you should do, what your partner wants, and all the supposed problems that you’re conjuring up, and do what you want to do. Babies rarely appear at exactly the right time and if you wait for ‘the perfect time’ you’ll find it never comes.
If your DD is 2, then this potential baby would be a good sibling gap for her too.
Whatever you go on to do OP, I wish you and your family all the best for your futures. It seems like you are putting all your thought into this and doing your absolute best.