1) Amanda knows that Meredith has 2 phones but only calls one. Two possible reasons: Amanda is in a hurry or Amanda knows that both phones are in the same place.
A lot of your points here are based around the incorrect notion that there was some sort of manhunt going on for Meredith (and your hindsight in knowing that Meredith was murdered). Until Amanda and Rafaelle returned to the cottage and saw the broken window and Meredith's locked door there wasn't much reason to think anything sinister had happened to her. This is also backed by Filomena and Amanda's testimonies that show their first conversations were primarily about the unusual state of the cottage, not "Where the h*** is Meredith?".
But, anyway, to address your first point... Those aren't the only two reasons Amanda would only have called one of Meredith's phones. Again, you're thinking in terms of Meredith being missing and that Amanda didn't do all she should have to locate her. In reality, and according to her testimony, upon leaving the cottage the first time her instinct was to get a hold of one of her roommates to let them know what she found, of which she had three. She tried Meredith first, since they were closest. Meredith didn't answer, so she immediately calls the next roommate in line, Filomena who tells her Laura is in Rome. This is perfectly logical.
2) Amanda didn't want Filomena to know that she had already called Meredith first and doesn't want the rest of us to know this either.
A baseless assertion. You only think this because you think she's guilty. As I've mentioned above, Meredith was not a conversation piece at that point. And it also makes no sense that Amanda wouldn't know "we" would find out about all the calls she made.
It's hard to believe that their discussion of trying to locate Meredith wouldn't have caused Amanda to remember that she just called Meredith.
Their discussion was not about trying to locate Meredith.
Meredith's Italian phone was registered in Filomena's name, so if the phones had been found there would have been a chance that Filomena already knew that something had happened to Meredith before Amanda called her. Calling one of Meredith's phones would have been a way to find out whether they had been found (going over to the garden would have been too risky).
This one is kind of confusing. Are you saying that because the phones may have been found already that calling both would somehow not be incriminating, or that by calling one she was able to establish that the phones hadn't been found (when actually they had been)? I'm sorry, you'll have to explain this one better.
3) Amanda claims that one of the Meredith's cellphones rang for a little and then there was a "disturbance". She claims that the other phone "just kept ringing". For Amanda's story to be believable, we would have to believe that both phone companies had problems with their voicemail at the same time. It would be easier to believe that one company had a problem with their voicemail and there was something wrong with the other phone, so it would have been in Amanda's best interest to mention the "out of service" message. Amanda's actions and statements are consistent with someone who hung-up as soon as the phone calls went through, but her story implies that she was not able to get to Meredith's voicemail. This one should be obvious.
Hers tory is the same as Filomena's:
"I tried to call Meredith right away. One of the phones rang but no one
answered. The other was turned off," said Filomena.
Also, the police had removed the sim card from one of the phones which, according to a quick google search, will stop service of voice mail or result in an "out of service message", depending on the provider.
4) If Amanda had revealed that she waited until after Filomena had called her to call the police (and waited 17 minutes - and Raffaele was with her, so excuses like she didn't speak Italian well or that she didn't know how the police in Italy work aren't credible), she would have to explain why after discovering that the cottage was broken into she neither called the police nor any of her roommates.
Rafaelle called his sister who was the police. She advised him to call 112 so someone could be dispatched. Filomena called minutes within them returning to the cottage and discovering the broken window and locked bedroom door. If you're going to criticize delayed reactions and hesitation to immediately call the police then you have to also find fault with Filomena's slow response times as well.
Amanda's poor memory was not confined to phone calls. She also "forgot" that Raffaele had not slept in until ten. And she "forgot" that she and Raffaele had eaten dinner around eight the previous evening rather than the ten or eleven that she claimed. One would think that she could remember at least a few of the things correctly.
And this proves that what? She has all-around poor memory? The problem with all of your points is that none of them actually prove anything since her actions all have positive and (barely) negative connotations, depending on how you look at them. It's not like we're talking about Casey Anthony who didn't report her child missing for a month. We're talking about a difference of a few minutes over what you think should have been a reasonable response time to certain events, and mistakes in memory that another roommate has proven to have been just as guilty of.