1: what's something that your girlfriend wants/needs? A bike, a computer, how about a silver necklace. Go buy it for her and give it to here. It should cost you about $1,000
2: When you give it to her, tell her you are taking her on a holiday. You are paying. Spend the $4K on the holiday.
3: Do steps one and two NOW. Get up from your chair and do it now.
After this, you will have a very happy partner who will love you more because you put your relationship ahead of stupid business.
Alternatively you could spend your last $5,000 on one of your ideas or you could spend your $5K on someone elses idea. In either case the idea probably won't work, and even if it is a good idea it does not need your $5K. Your money will be gone. You will never have invested any substantial money into yourself/your girlfriend/your relationship which will fall apart because it's no fun and there's always money pressure and you are always stressed because you never have a holiday and are always working. You'll be in exactly the same position you would have been if you'd spent the $5K on her.
In the meantime, pursue your personal business ambitions as a hobby and stop gambling everything you have on it.