Woman going for hajj without husband's permission?

My friend has received her share of inheritage from her late father, some 3 years ago. The problem is that though she is rather well off she has kept that money to perform her hajj and now that her children are more or less settled down she wishes to go for hadj. But her husband agreed in a first place to perform the hadj this year, some weeks ago he said he can’t go for hadj now and need that money to buy a flat which is not a must for their living but merely an investment. So my friend wants to know must she agree to give her husband that money or can she as per sharia law refuse him and insist on going to hadj. To be noted that if they don’t perform hadj this year it might take them another 3-4 years before they go.