firstly, she will most likely not get into forensic science now, those grades are too low, it is too competitive, and what ever she does next, she will still have to declare those grades on her application.
Secondly, what the hell does she think she wants to do forensic science for, anyway? Its utter crap. I have kept in touch with three students who have done it. One spends her whole life at he same table in the lab, all day every day working her way through packets of animal hair, looking them under microscope, deciding which animal they most likely came from ( she one had bear hair, but 99% of the time it is dog), entering the data into the computer, and picking up the next one.
Another girl does the same except with jars of samples of vomit, and she normally tests 10 at once, and does a series of tests over about an hour and a half, then moves on to the next ten samples, etc, and that is all she does ever.
The other does something in the supply chain of weapons, doesn't get to see the weapons or anything, just reads data of the labels of packets reenters the data into the computer, and occasionally has to run into court to testify that the chain of custody was secure - won't hear what the case is about or anything, just runs in, gets questioned, runs out and goes back to the office and sits down and carries on entering data.
The reason it is so popular and competitive, is because of large number of largely pretty sheltered, not very clever or well informed, fairly inactive and immature teenagers watch a lot of american dramas and think it is something like that.
Whether your daughter can or can't redo the same subjects isn't down to persuasion or favouritism, or anything like that, it is can the school get funding for it ( probably not) and is there a reasonable chance she will eventually pass ( also probably not)
Her friend that got U and U might well have only been examined in one module, in subjects she already has better grades in other modules for.
As to asking for remark, you need to think carefully, I believe it is always worth a shot if you are really sure you won't get the mark put down, as long as you are not throwing away the money you need to eat with! Because of the possibility of always wondering "what if" if you don't. But she is not 1 or 2 marks away, she is 4 marks away, so closer to a U than a D, in all probability.
So,
That all sounds very negative, but the situation is far from negative.
She is a hard worker with a supportive mother, she is 17 and as three ( low grade) ASs under her belt ( and these will count for something in her UCAS application) and many schools will want her.
Please understand, I am not saying her current school WON'T want her, but due to the weird and wonderful funding formulas, it is easier for a school to get funding for a new student than one that has already performed badly in year 12)
Look around other local schools.
BTEC applied science is a good option for hard workers who want a science and maths qualification, it is highly respected by MANY universities, not all, and not many RG universities, but she is most likely not going to enter university education at that level anyway.
Biomedical science is a degree which opens many doors, (including forensic science jobs, sometimes) and there are many many courses, it is not particularly competative.
That is one option.
So she needs to apply to other local schools, and to return for enrollment at her current school to see what they are offering her.
She can accept more than one offer from sixthforms at this stage, as long as she decides quickly, and doesn't deliberately mess people around.
At the end of August, she might well find herself holding two or three different offers, and having to choose between them!
I would only suggest paying close attention to the advice from staff that know her, she doesn't have to take it, but it is more likely to be realistic than from other schools keen to get bums on seats rather than match students to courses too closely.
I have taken on many students in this situation, onto BTEC courses, and they have gone on to get university places and careers they enjoy, even though BTEC is often not first choice.
Good luck.