Sorry, I do think the HV is right to refer her.
Either she'll suddenly have a spurt and catch up, and you can refuse the extra help when you get to the top of the waiting list, or she won't, in which case you'll be very glad you got on the waiting list sooner rather than later.
You can help. I'm sure you talk to her, but did the HV explain to you how to help increase her words along the lines of:
Car
Yes, that's a blue car
Blue car
Yes the blue car is going fast... etc.
Pointing, try reading to her and asking her to find things in the pictures. "Can you point to the flowers?"
Thing is to remember that you only have your dc to look at. The HV will see lots, so it is easier for her to be able to see if things are a bit unexpected. But some children gain quickly at times, and slower at others, so you may find in a year's time she's more than caught up.
Edited after seeing your last post.
Being referred won't harm her; if the waiting list is 6 months, for example, if she's caught up at 2.5yo then you can remove her from the waiting list. But if she's fallen further behind at 2.5yo, then you're now waiting until 3yo for intervention when really the sooner the better.
I really wouldn't ask to come off the list at this point.