I took 10 suitcases with my stuff haha (some was my husband's as he flew out to fly back with me as I'm terrified of flying, but mostly mine). I didn't declare anything at all as it's all personal effects so she should be fine
If there are any newer items, I would suggest maybe just removing all tags to suggest so and maybe not carry all the cash she owns on her (as I know over a certain amount of money you need to declare so would suggest other methods for that), but that's just me being overly cautious as nobody even checked! I went through customs in the UK line as I was with my husband and by the time we got our bags nobody was even there asking questions. If they had, I would've just explained. Don't worry! She'll be fine!
She will just maybe need a hand with her bags if she packs like I did! haha