Can an adult child who is executor of an ill parent's estate contest a no-contest clause in a living trust?

If so, on what grounds? And if same parent with no-contest clause has been willingly giving money & paying bills for another adult child off-and-on long before parent ever became ill, can the executor challenge the no-contest will/disinherit later because of $$ help the parents gave her? Ill parent is of sound mind, speaking, functioning still. The executor is financially very successful, but the other adult has recent foreclosure, divorce etc... They do not get along, or have much of a relationship at all and never did as they have different fathers and a big age gap between them. Both sisters routinely help parent with grocery shopping, doctors appts, etc. The executor recently attacked the other sister verbally & viciously in front of parent, name calling and hateful words, and does not agree with parent helping the other sister. The executor is WORKING with estate lawyer of ill parent to track down properties & assets of said parent's deceased spouse (who passed away recently), 'tying up loose ends' and taking over parent's home paperwork, paying parents bills from parents own money, prepping to be executor, while ill parent knowingly continues to help the other sister pay her own bills. Can this financial help be used against the other sister later to change the no-contest clause or challenge their equal inheritance? Ill parent with no-clause trust says it's her money and she will help daughter if she wants to like she has had to for some time.