A nice idea, Lumutqueen, but we actually do not know this. Under English law, Trusts are private and the terms of the trust are governed by a Trust Deed, which is a private legal instrument. Generally, there are two elements to a trust, income and capital. There are very often restrictions on the use of both income and capital. It is common with some trusts to prevent the beneficiaries accessing the capital until they are 25 years old or so. We don't know what the terms of Beatrice and Eugenie's trusts are. There may well be strict clauses about use of the money - athough thanks to Sarah, we know that apparently the restrictions on the use of trust income were lax enough to allow Sarah to 'leech' [as the papers put it] off her daughters' trust funds. I believe Lord_Royal is a solicitor; perhaps he could help us with English Trust law if he drops by here.
Indeed, I am. The trust for Beatrice and Eugenie that Sarah has spoken of is the one made for them by The Queen when Andrew and Sarah divorced. Now, something murky happened in the late 1990s regarding the 500,000 pounds budgeted for a home for Sarah and the girls (the house in Windlesham was said by Sarah to be too expensive to run, so a house was never purchased) and I recall Sarah had a meeting with the trustees of the the B&E trust. I wonder if that 500,000 was added to the trust. ANYWAY...
There is usually two components to a trust: income and capital, both of which can be managed by the terms of the trust. From various articles we know that 1.4 million pounds was put into trust in 1996. Since that time the money has surely generated a substantial income. The trust instrument would explain if and how that income could be spent, the lifespan of the trust and other conditions. The simple fact of the matter is that there is absolutely no way to discern what the trust says since it is a private document. What can be said, without hesitation, is that Princesses Beatrice and Eugenie cannot do as they please with the trust money, they will always have trustees to answer to.
However, the trust will be wound up (as all trusts have a determined lifespan, they cannot go on indefinitely) and at that point the Princesses will have free reign over their funds. Additionally, Saunders v Vaughtier tells us that an adult can collapse their trust at will. As both Princesses are over the age of 18, this may have occurred.
It's also worth keeping in mind that the Andrew and Sarah Divorce Trust 1996 is not the only trust B&E are beneficiaries of. The late HM The Queen Mother established trusts in 1994, totaling 19 million pounds (the vast majority of her cash) for the benefit of her grandchildren so that none of them had to pay any taxes or duties.
So there are certainly two trusts that benefit the York Princesses. There could be as much as 6 million pounds of capital in The Queen Mother 1994 trust for the York girls. We'll never really know.
They should focus on charity and enhancing their image. The role Princess Alexandra fills would be ideal for them.