The problem at the moment is that we just don't know and people can't wait forever for us to know.
In terms of research funding, the government is committed to underwriting the current Horizon 2020 funding, but not the ERC or Marie Curie funding which we will become ineligible for at the end of March if we leave with no deal. This could lead to immediate job losses. We know nothing about what will happen for the Horizon Europe funding that will follow the 2020 funding and that we should be gearing ourselves up to bid for now. The longer we wait, the more likely it is that our partners will have to move on without us, whether we ultimately reach a deal to pay in as an associate country or not. If we decide not to pay in, people will be reliant on whether the government regards their research as a strategic priority and funds them or not. Given what we have seen of the government priorities so far, we can guess who the winners and losers will be in that scenario.
The impact of the potential loss of funding will vary a lot by discipline and department. My own department gets about a sixth of our non-core research funding from Horizon 2020. We probably could replace that amount with alternative funding if we missed out on Horizon Europe and we have a strong enough reputation that we have been able to enter into provisional 'dual national' agreements with two European universities that would allow us to go into European funding bids as employees of those universities if necessary. This would not be ideal for our university or our staff, but would ensure the continuation of our research in the short to medium term. However, we currently have European funding for six PhD places, and we would be unlikely to get that from elsewhere.
The situation is a lot more worrying for other departments and research groups and the expectation is that some will fold through a combination of loss of research income and loss of key staff. So far, we have lost two EU staff. They aren't irreplaceable, but they are a loss. We are still waiting for formal clarification on exceptions for recruitment of new post doc and early career lecturers from outside the UK. Nearly half of our academic staff would not meet the pay threshold to be considered highly skilled.
There is also a concern that universities will use uncertainties over Brexit to sweep away some of their less favoured staff and departments, particularly in the lead up to the REF, and we will see redundancies in areas that are not directly affected by the loss of European funding as part of a broader strategic exercise.
Overall, the most likely scenario is that we will eventually come to an association agreement that will secure much of our research funding, but not all of it. The biggest risk will be the loss of the UK's ability to lead research and determin European research priorities, and the reputational damage that will gradually come with that and our inability to attract and retain the best staff.
In terms of your own DD's prospects, as others have said, the route into a permanent job has always been an uncertain one and that will be the case regardless of if and how we leave the EU. She needs to be realistic. Focus on getting funding for her PhD if that is what she wants to do (is she not leaving this a bit late?). Beyond that, unless she is in a very vulnerable research area, Brexit is low down the list of her concerns.