BOTH need to be spayed/neutered before introductions. Rabbit fights can get extremely vicious and rabbits that have not been altered are more likely to fight. Leaving even one unaltered can be extremely dangerous to both rabbits.
The main thing you need to consider and think about is: do you have the time, energy, and patience to bond them? AND will you have the time and energy to commit to a 2nd bunny if you cannot get them to bond?? Rabbit bonding can be very stressful and I would definitely urge you to research more about what it takes to bond before committing to a friend for your rabbit
I also need to comment that if you do not have the money to alter another rabbit – are you sure you are financially stable enough to care for another rabbit and their potential vet bills? Not saying you don’t… just something you definitely need to consider before making a final decision!
I will add – ignoring each other during bonding is actually a good sign! If you think you can spay the other girl as well, she MAY be a good candidate for bonding to your current bunny. I will also add, you may need to inform your friend that an unspayed female has an 85% chance of developing uterine cancer before the age of 4. Spaying is essential to ensuring a healthy, female rabbit. It’s incredibly important for females!
As for having multiple rabbits…. rabbits with friends is amazing! I have a bonded group of six and I absolutely love the connections and relationships between them. However, rabbits can be happy rabbits single AND it’s much more important that you ensure you have the ability and funds to care for your first rabbit AND the money and time to commit to a 2nd. You will be doing NEITHER any good if you find it’s much more difficult to care for and more money with two!